Hi all,
I thought I'd quickly introduce my latest project. Below is a picture of a very early prototype I built tonight. As the title implies I've called it the 5VCPC and that's more or less what it does. It's more of a solution to an issue rather than an expansion. The device solves two issues by doing one thing - creating a 12V supply from the 5V rail, so:
1) It allows a Classic CPC6128 to work without needing a 12V supply. Neat desk, no pigtail hanging out of the CPC, only one PSU.
2) It also allows you to use a standard 5V/12V PC drive or CPC 3in drive in a CPC6128+ without having to add a 12V PSU.
The plan is that it can be installed inside the CPC without any soldering or even needing any fixings. The PCB plugs directly onto the back of the disk drive and the normal power connector to the drive plugs into the 5VCPC PCB. This first prototype was to test dimensions and confirm the function, however, I messed up on the dimensions, so it's slightly too tall and doesn't fit in the CPC with the top in place, but that will be sorted on the next prototypes. This time around I just want to confirm that it works and test:
- How much power it pulls from the 5V rail.
- How hot it gets.
- That it doesn't disturb the 5V rail / make the CPC crash.
- That it doesn't transmit all sorts of shite that makes everything in the room crash or cause distortions on the CRT / Display.
- That the drive actually works when powered from it.
- The circuits efficiency.
I'll be doing the first tests this weekend and when it passes everything, I'll be sending one to Villain who has offered to use it for real and give further feedback from real use.
Bryce.
Very useful device. I will be getting one or two of the final version, probably two :D
That is awesome indeed! Very useful specially if you connect your CPC, say, to a 25" Sony Trinitron CRT [emoji4]
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I think that peoples using a CTM will have to continue to use +12V to avoid dim light when to FDD motor start.
But it is nice with an external +5V power supply instead of a dual voltage external PSU. (like provided with 3"1/2 HDD case)
What 3.5in drive do you mean? Or did you mean the standard 3in plus drive?
A standard CPC6128 needs 960mA on the 5V rail in idle with no expansions attached. The 5VCPC will need about 700mA extra, so almost 1.7A for an idle machine. So the PSU will of course need to be powerful enough. 3A would be a good number to start with.
However, regarding the dimming of the screen. This may not be an issue of not enough amps. It could also be a problem with the power rail design not being able to react fast enough. ie: The PSU might have enough amps, but can't adapt fast enough to a sudden rise in required current. These are all things that I will be looking at before I ever release any final product. There are ways of improving or even completely removing this problem.
Bryce.
I have seen that on CPC using a 5V "Y" cable to power an external 3"1/2 PC floppy drive or with a hacked internal drive.
But I think it was mainly because the CTM was tired... I have fixed the problem with a 12V to 5V converter for the floppy drive.
I'm not sure I fully understand you. Almost all PC 3.5in drives use the 12V rail for it's motors.
Bryce.
As I know, most PC floppy drives are +5V only. ;D
I never seen a PC drive using the +12V, either. Only old ones found in Amiga, Atari or Thomson machines.
And yes, the result when using those powered from the CTM +5V supply is that the CTM will be darker when the motor is spinning. Probably not a good idea to do so.
That must be a French thing. I have 5 PC drives here and all of them use the 12V rail. Either way, as I said, the screen going dark during disk access is due to bad design, I will make sure my device has been tested for this.
Bryce.
That is interesting, as I have a pile of 10, 3.5" drives from various manufacturers (Mitsumi, Sony, Panasonic...), and different years of manufacture, from mid 90's to mid 2000's and they are all 5v only.
Cheers,
Shane
I'll check them all again later, but I'm pretty sure they are all 12V/5V. They are of course 720 drives, none of this fancy modern 1.44 gadgetry!
If they're not as common as I thought, then I only need to include one header on the PCB and go back to it only being for the Classic CPC.
Bryce.
This is really interesting and useful if it turns out it works :) (and if it does the question will be, of course, why didn't Amstrad do it in the first place?)
Quote from: Gryzor on 14:52, 09 December 16
(and if it does the question will be, of course, why didn't Amstrad do it in the first place?)
Cost issues, of course!
The bottom line was the most important thing at Amstrad :laugh:
Yeah, it was mostly rhetorical :D
They did something similar, but decided to put it in the CTM rather than the CPC. For several possible reasons:
- Cost saving: having the 5V and 12V power supplies at the same place means they can share some hardware
- Lack of miniaturization: power supplies today are much smaller than they were in the 80s
- Power dissipation: anyone who saw a Thomson TO7 with the huge heatsink on the back knows what I mean
Quote from: PulkoMandy on 17:24, 09 December 16
They did something similar, but decided to put it in the CTM rather than the CPC. For several possible reasons:
- Cost saving: having the 5V and 12V power supplies at the same place means they can share some hardware
- Lack of miniaturization: power supplies today are much smaller than they were in the 80s
- Power dissipation: anyone who saw a Thomson TO7 with the huge heatsink on the back knows what I mean
Err, yes and no.
The CRT monitor already includes a type of switch mode power supply. So why have another for the computer?
The technology did exist, yes, it would have been larger than today's technology. But there was space in the case if Amstrad had wanted to do it that way. Remember, the Acorn Electon has a low voltage switch mode power supply inside the computer case.
Mark
There's no DC/DC converter in the CTM, they existed at the time, but they were extremely new (invented in 1977) and there were no dedicated ICs available, it would have had to be done with discrete components. That doesn't mean it would have been out of the question. The humble Spectrum 48K has a DC/DC Booster circuit to provide 12V from the 9V supply.
What always puzzled me, is why they didn't just have a 12V connection from the monitor and derive the 5V from that. It would be the identical components that they used in the monitor, just on a different PCB and they would have saved a cable and connector = cheaper.
Bryce.
You're thinking about the CTM644.. what about the CTM640?
CTM644 is still useable on a 464 and because that never needed 12V I guess they added it as a second cable to keep compatibility?
Quote from: Bryce on 22:45, 05 December 16I'm not sure I fully understand you. Almost all PC 3.5in drives use the 12V rail for it's motors.Bryce.
Nice project Bryce, but i find you a bit "uninformed", regarding the power supply of 3.5" PC floppy drives :)
For 20+ years now, ALL 3.5" floppy disk drives use ONLY 5volt power supply, for the board, the step motor and the plateau motor (btw, remember that 6128+ introduced on 1990, had even his 3" disk drive, with 5volt supply only?). I happen to know this because i've tested dozens of different 3.5" disk drives (some where 15-20 years old), and haven't found a single one that needed 12volt supply too. And that's why the Y power supply cable i make for powering Amstrad and 3.5" disk drive gives only 5volt( and the fact that after selling 100's of them, no one ever complained for a disk drive not working seems to "confirm" that ;) ) . I think that only VERY old 3.5" disk drives (from early 90's or older) might need 12volt supply too, but i doubt you can find many owners of such 3.5" disk drives any more....
Having said that, i wonder, how old might be the 3.5" disk drives you said you have, and need 12volt supply too? :)
I've still got some 3½ drives with 12V motors. They are all single or double sided DD drives. I have not checked all my HD FDDs, but they may well all be 5V only.
Mark
Single or DD drives you said? I suppose from mid 80's or something, right? :)
And yes, you are probably right that perhaps all HD drives need 5volt only, as they were more recent than DD drives.
IMO, i tend to believe that almost all 3.5" disk drives manufactured after ~1990 needed 5volt only. Even with amstrad 3" disk drives,i have noticed that early models (from 1985) had 12volt step and plateau motors but later 6128 models had 3" drives equipped with 5volt step motors instead! And also, don't forget that 6128+ released in 1990, had even his 3" drive with 5volt supply only.
The drives that I speak about are either ex-Atari ST drives, ex-Amiga drives or were obtained between 1988 and 1993 approximately. Note most were not retail "new". Some came from surplus electrical companies. Then there was a gap when I did not buy any. Then found that DD drives were no longer available, so got HD drives.
Mark
I went back and checked the drives. 1 of them is a 5V only drive, the other 4 are all 5V/12V drives. They all came out of old PC's from the 80's that I dismantled a few years ago. I also found 3 other drives from more modern times and they are all 5V only drives, so there seems to be a cut-off date when drives went from being 12V/5V to being 5V only.
So yes, @ikongrs: seems like I am a little uninformed when it comes to 3.5in drives, I didn't know that drives became 5V only at some time, but then again, I don't have a lot to do with 3.5in drives and I don't think I've ever bothered fixing one. I just throw them away and get another one.
I'll change my 5VCPC schematic and layout to only handle 3in drives.
Bryce.
A quick update on my 5VCPC project. I finally got around to finishing all the tests and here's the results:
DC/DC converter 5V side:
Uses 11mA with no load
Uses 119mA with disk drive in idle (an idle disk drive pulls 39mA from the 12V supply)
Reading/Writing to a disk requires 313mA (with a very old drive with dodgy motor it can have peaks of up to 500mA)
12V Side:
The normal 12V disk drive supply uses 39mA in idle and uses between 110mA up to 200mA on older worn drives.
The DC/DC converter is running at around 87% efficiency. I've designed it to supply up to 400mA so technically it would be able to supply two drives at the same time. It's only disappating a few mW, so even with constant usage it will never get even slightly warm.
Regarding the potential EMC/EMF issues mentioned above: No, it doesn't interfere with the CPC in any way, no crashes, no issues and no screen flickering during loading. All real-world tests were done with a Spectrum +3 2A 5V supply. The standard 6128 needs around 1.1Amps for the computer alone and with my DC/DC converter you should allow for an extra 500mA for the DC/DC 12V rail, so a 1.6Amp supply would be enough to power a 6128 with no further expansions.
Next steps: Despite my fancy design, I will need to change the layout and move away from the idea of mounting it on the back of the drive. It's very wobbly and there's a risk of shorting out against the metal drive parts. So the final design will be a small PCB with a flylead to the drive.
Bryce.
P.s. If anyone is interested in converting their 6128/664 to a 5V only device, then let me know here so that I can judge how many PCBs I should make in the initial batch.
I'm interested in one for sure!
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Quote from: robcfg on 18:18, 31 December 16
I'm interested in one for sure!
Sent from my iPhone using Tapatalk
My Order tracking template in Excel automatically includes your name at the top of the page :D
Bryce.
Quote from: Bryce on 19:03, 31 December 16
My Order tracking template in Excel automatically includes your name at the top of the page :D
Bryce.
:laugh:
Please add my name as well :D
Mark
Add one to the list for me, please ;D
Haha Bryce, you know me too well! :D
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I've re-visited the layout issues and I may have a solution to keep it mounted on the back of the drive. If I move the input capacitor to the back of the PCB it not only reduces the size of the device, but also acts as a standoff to avoid anything shorting against the drive metal.
Regarding the interference tests above, I should also mention, that this prototype doesn't even have a proper groundplane, so the end device should perform even better. I left the prototype running over night with a transient load switching between 150mA with 1mS 400mA spikes once per second to simulate bad case real usage. The device is still happily running this morning and still at room temperature :) I just need to check whether or how much 5V rail spikes it produces on a real CPC and then the design is more or less finished.
Bryce.
I'm interested Bryce, please add me onto the list for 2 boards.
Andy
Yesterday I optomised the layout further, mainly so that I can squeeze the device into the tiny space behind the drive on a 6128, but also to "balance" the PCB better so that it sits nicely on the back of the connector. To do this I had to move some components to the back of the PCB which also had the bonus effect of making the PCB even smaller. I've ordered some prototype PCBs to confirm the design and I'll be building them probably late next week. Here's what the (possibly) final design looks like. The board is now just 40mm x 24mm.
Bryce.
It really looks beautiful!
I've just ordered the parts for the mini-batch. The 5VCPC will cost €24. I will only be building 15 of these, so if you want one you'll have to be fast.
Bryce.
That is without postage, right?
I think that i will ve taking one, if that is possible :) .Yesterday I found my original CPC 6128 and, although the guy is pretty battered, I would love to fully restore it and install the adapter on it :D
Quote from: robcfg on 15:40, 04 January 17
That is without postage, right?
Yes, because postage will depend on where you live. However, it's pretty small and light, so postage shouldn't be much to anywhere.
@||C|-|E|| (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1447): You'd already stated interest in one or maybe two on the first page. Is this an additional one or how many do you want in total?
Bryce.
Sorry! it is the same one i wanted to have. This memory of mine... :picard2:
If you ordered a small batch, one should be OK. This way more people will be able to have it :D
I can use one of these. Put me down for it, postage to the UK.
Cheers
JonB
Hi all,
as the price of my 5VCPC has been called into question, I'd like to go through the design process step by step and explain why my device is not a $1 Chinese DC/DC converter and why my device costs what it does. For obvious reasons I don't have the scale of economics that the Chinese manufacturer will have, so I think everyone knows why it doesn't cost €1, but I'd like to explain the rest of the costs to you too. One point that needs to be explained up front is that a DC/DC converter is NOT the same as a digital expansion. It's not just the values of the components that are important, but the type, manufacturer and quality of the components all have a huge effect on whether the circuit works at all, disturbs all the electronics around it and runs stable and efficiently. On a typical digital expansion the designer will usually add a 100µf cap and maybe some 100nf decoupling capacitors. The type and manufacturer of these makes pretty much no difference, so you can choose the cheapest you can find and be pretty certain the circuit will work anyway. You can't do that with a DC/DC converter.
So here's the breakdown:
Mounting Location:
As you can see, the device is mounted on the back of the floppy drive, where there is exactly 10mm space. This obviously restricts many things and increases the chances of a short circuit. It's not mounted here because it looks fancy, or because I thought that would be cool. It's here because DC/DC converters transmit all sorts of crap that can disrupt and even crash the CPC, so it's important that the device is here hidden behind as much metal as possible and not right beside the mainboard. Unfortunately it also restricts what parts I can use because everything has to fit into this tiny space. The Chinese converter is considerably bigger and would not fit here.
PCB:
Due to the mounting position and shape a custom PCB was required. The PCBs cost me €5.80 each plus postage because I ordered just 15 boards which is considered mini-prototype volume. I could have ordered 100 PCBs instead of just 15 and the boards would have cost a lot less, but I won't sell 100 boards, so why order that many? I could also have got some chinese sweatshop to make the PCBs for a lot cheaper, but I believe in supporting local jobs, so the PCBs were made by a company whose manufacturing plant is in Ireland.
The regulator:
Why didn't I use a cheap adjustable regulator?
The Chinese devices use variable regulators which are relatively cheap (about €2 each). However, these have several problems:
- It needs to be trimmed / setup by the user to the exact voltage required and most users don't own a multimeter.
- They tend to drift with temperature so the voltage level is not always the same.
- I don't have space for a trimmer behind the drive even if I wanted.
- They are not optomised for 12V so their efficiency varies depending on what you set the voltage too.
- But most important: They have a failure mode, which involves shorting just one point on the PCB, which could easily happen in a space as tight as this. In this failure mode, the DC/DC converter can output more than 35V instantly, without warning. You don't have to be an electronics expert to know that this wouldn't end good for your floppy drive. Something that I definitely wouldn't sell or advise a CPC user to put in their computer.
Because of this, I went for a fixed voltage regulator, which (due to the fact that the IC contains precision resistors which an adjustable regulator doesn't), these cost quite a bit more. Not only that, I went for an older type that switches at a lower frequency than the more modern ones, again to reduce the noise being created. Using a newer type would have meant I could use smaller capacitors, but also mean that I would need to shield the entire PCB which I have neither space for, nor would it have been financially viable. In this case, the regulators cost me €5.50 each including postage as I could not find them locally and they are a relatively difficult part to source.
The inductor:
There are several grades of inductors available. You can use the small resistor type versions. These cost pennies, but they can't really handle the current required here. There are larger inductors wound on a ferrite core that can take the current and cost maybe 60 to 70c, but they are unshielded, so they transmit crap all over the place. I chose a shielded ferrite type, but not only that, I went up one step in the current capabilities which further reduces the amount of crap being transmitted and ensures that the inductor never gets hot. These cost €1.20 each, but they guarantee the least chance of any disturbance to your CPC.
The capacitors:
The capacitors on a DC/DC converter are pretty much the most critcal part of the circuit. To work properly, these should be high quality low ESR* parts. In fact many regulator datasheets will specify both the manufacturer and part No. that you should use. The Chinese devices slap on any old capacitors, not even low ESR most of the time and usually a lower value than is recommended. A typical standard capacitor will cost a few pennies. A low ESR capacitor will cost a bit more, then there are capacitors that offer a longer lifetime of up to 10000hrs and these cost more again. As any Amiga owner will tell you, capacitors don't last forever, so the longer lasting ones have a real advantage. I chose to go for a longlife, very low ESR part. Unfortunately these are usually 10mm wide barrels in the value I wanted, but I only had space for about 8mm as the PCB is 1.6mm thick and the total free space is 10mm. For this reason I also had to go for a slightly more expensive low-profile version.
The capacitor I chose in the end costs 95c each. A regulator datasheet gives a formula to calculate the value of the output capacitor. In this case the value came out as 560µf. However, I went for a larger 680µf capacitor because the disk drive 12V load is what's known as an inductive load and because it doesn't pull a steady current from the supply. This means that not only does the current get pulled in short bursts, but also that the current demand is out of phase with the voltage rise. This is something that DC/DC converters don't like and needs to be addressed. I partially counteracted this by increasing the value of the output capacitor.
Although the input capacitor does not need to be low ESR, I decided to use one anyway. The reason for this is that DC/DC converters also cause spikes on the 5V (input) rail. These are going directly to the CPC mainboard. The 5V logic on the mainboard can live happily with up to 5.25V and will (for a while) survive with spikes up to 5.4V, however, if the 5V rail is going above this every time you access the drive, your CPC will most likely have died within a week. I have measured spikes of up to 5.45V on a chinese DC/DC converter. My device doesn't produce spikes above 5.15V. A further 100nf capacitor on the input filters out higher frequency spikes.
The schottky diode:
Another important component on the DC/DC converter. I could have saved some money here and used a cheaper SMD part, however the smaller SMD part would have produced more heat than I wanted, so I went for a large thru-hole part. Heat is important on this PCB as all three "heat producers": The regulator, diode and inductor are right beside the output capacitor and capacitor lifetime is inversely proportional to the temperature of the environment it is working in. The diodes cost 35c each plus postage.
User friendliness:
Most users probably don't own a soldering iron, nor do they want to be cutting wires or tracks in their CPC. For this reason I wanted the device to be completely plug and play with no soldering required. This meant adding the correct socket and plug to the PCB, which obviously a chinese converter doesn't offer. Although I was able to use a readily available plug, the socket is an obsolete part, that again I had to find an alternative source for and pay premium prices to get (€1 for socket and 32c for plug) and again pay postage for as it is yet again a different source.
The remaining parts cost just pennies and aren't worth mentioning. However if I may sum up:
PCB €5.80
Regulator: €5.50
Inductor: €1.20
Capacitors: €1.40
Diode: 35c
Connectors: €1.32
Other passive parts + solder etc: 50c
This is already over €16. It doesn't include some of the postage costs as I had to source the parts from 7 different vendors. It doesn't include the costs of the any of the other regulators / inductors / diodes etc that I bought to try out during the development. It doesn't include the costs of making the prototype PCBs seen in the earlier pictures. It doesn't include anything for my time and effort, nor for anything getting lost in the post or breaking.
As you can see, I put a lot of time and effort into ensuring that this device does what it should, does it safely and efficiently and won't destroy your CPC. My aim isn't to make cheap devices, my aim is to make high quality, good performing, safe devices for the CPC.
This may not be appreciated by everyone, but if anyone still feels scammed by the price I have put on this device I would be very happy to hear from them.
Bryce.
* ESR stands for Equivalent Series Resistance and more or less just means how easy AC voltage flows through it. The lower the better in a DC/DC converter which has lots of AC that it needs to be canceled out.
That is a nice and detailed explanation, thank you!
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So, I just got my hands on one of the Chinese DC/DC converters and thought I should share this data with you.
The following screenshot shows the spikes this device feeds into the 5V rail of your CPC if you were to install one in your CPC. In the first screenshot the DC/DC converter was supplying a constant 200mA load.
[attach=2]
As can be seen from the screenshot there are regular spikes of up to 5.6V on the 5V rail.
The next screenshot was taken while the converter was connected to a transient load switching between 100mA and 200mA to simulate reading a disk.
[attach=3]
The spikes have now increased to 5.68V
The TTL chips in the CPC are specified to work up to a maximum of 5.25V. I can't say for sure how long the CPC would survive this abuse. Not very long I suspect.
Bryce.
I'll take one if you have any left in the 15 batch @Bryce
Happy New Year & I am sorry for the late reply :)
I am also interested in one Bryce!
Thanks!
Thanks guys, all orders noted.
Bryce.
Quote from: Bryce on 10:58, 06 January 17
...if anyone still feels scammed by the price I have put on this device I would be very happy to hear from them.
Bryce.
Scammed...If anyone felt scammed then they can go design/source their own... nobody is forcing these on anyone. :D
Cheers,
Shane
Just for the record. If I thought for one second, that a $1 Chinese device was suitable and safe to use in a CPC, I'd be the first to open a thread explaining how to install it and wouldn't have gone to all the bother I've gone to.
Gesendet von meinem Motorola DynaTEC 8000X mit Tapatalk.
Let's cut to the chase here. Been reading this sorry tale and I'm going to say just this on the entire sad affair.
There are people who believe you can buy any old cheap shit and use it. Cheap PSU's, cheap car tyres, cheap meat, whatever.
The cheap PSU will be a fire risk that could damage your device. The cheap tyres won't handle as well or stop you as fast. The cheap meat could turn out to be horse or donkey slaughtered in an Eastern European country with poor animal welfare. Etc. etc.
The people who buy this crap always know better. "Oh I only paid 40 quid a corner for my tyres", "Oh I get my meat from that cheap supermarket", "Oh I found a PSU on Ebay".
They are idiots. Pure and simple. It's always about how cheap it is with no other thought.
To do things properly is never the cheapest way. Just because something looks OK on the surface doesn't mean it is. We're working with vintage hardware here guys. It's fragile. You don't need to be an electronics expert with a scope to know some cheap bulk buy from AliBaba isn't going to be very good for elderly circuitry which needs a nice smooth supply.
Bryce shouldn't have to defend himself or post pictures of his scope. You want to go stick some shit Chinese adaptor in the back of your CPC, go ahead. 6 months later you'll be whining on here for replacement chips for your broken CPC. Anyone who isn't a complete moron will buy the proper solution from Bryce because they'll know you need a smooth supply that doesn't put your hardware at risk.
Which is exactly the same reason why I wince at people using cheap PSU's on their CPC's compared to the more expensive units with proper data sheets from the likes of RS.
Components cost money, the software to design the circuits costs money, the equipment costs money. I know people who design and sell very popular lines for other micros. You have to be able to fund the components, the wear and tear on your equipment and have enough left over for your running costs and to go towards your next project. If you think anyone should churn out projects for just the cost of components then you are a fool.
That's my 2p to the forum 'drama'. I won't make further comment.
One more thing that I think is important to mention. I'm not in any way saying that the chinese device does not do what it claims. It will convert 5V to 12V and is probably useful for certain situations, however, most DC/DC converters, even the more expensive ones are designed to give a good output voltage, the more expensive ones will give better results than the cheaper ones, but they rarely care about the input side of the DC/DC converter, for the simple reason that these converters are usually used in the following situation, where spikes on the input are pretty much unimportant.:
Source -> DC/DC Converter -> load (Sensitive electronics).
The situation in the CPC is completely different as there are sensitive electronics connected directly to the input side too:
Source -> 5V Sensitive electronics (mainboard) -> DC/DC Converter -> 12V floppy.
In cases like this, the spikes on the input become extremely critical as they can destroy the 5V electronics and need to be taken into consideration. I have looked for a generic DC/DC converter which claims to suppress voltage spikes on the input side in their specs, but I haven't found one yet. The main differences of my device involve improving the level on spikes on the input, the output voltage of my device is not all that much different than a generic device, other than that it was designed with an inductive load in mind.
The generic devices I've tested so far create up to 700mV of spikes on the 5V rail, easily enough to destroy a CPC mainboard. My device creates no more than 150mV on the 5V rail, even with an old crusty drive connected to the 12V side.
Bryce.
Update: The PCBs arrived last night. I'm still waiting for some other parts, but I have enough parts to make one. As soon as I have time to solder one up, I'll post some pictures of the final device.
Bryce.
Managed to find time to solder one up tonight. Here's what the final device looks like. Over the weekend I'll be testing it to the extreme to find out exactly where the limits are.
Bryce.
Result! It looks so professional... (but of course :D )
Nice!
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Quote from: Bryce on 22:13, 13 January 17
Managed to find time to solder one up tonight. Here's what the final device looks like. Over the weekend I'll be testing it to the extreme to find out exactly where the limits are.
Looking good :D
No, wait! Something's missing. A vital part is missing :o
Here (https://www.aliexpress.com/item/QC-Passed-self-adhesive-labels-qc-passed-sticker-labels/32373847687.html?spm=2114.40010308.4.62.pyd7lQ), that's what's missing :P
Mark
Very nice! :D There are some big caps in there :)
Quote from: 1024MAK on 01:29, 14 January 17
Looking good :D
No, wait! Something's missing. A vital part is missing :o
Here (https://www.aliexpress.com/item/QC-Passed-self-adhesive-labels-qc-passed-sticker-labels/32373847687.html?spm=2114.40010308.4.62.pyd7lQ), that's what's missing :P
Mark
Still doing the QC at the moment, so the stickers can't go on yet :D (Unlike Chinese devices that get the sticker without ever having been tested).
Bryce.
Parts arrived at the weekend and I was able to build a few more devices to do parallel testing. One is installed in my 6128 which my son is "testing" intensively with his favourite games - Sabre Wolf, Jet Set Willy, Harrier Attack and Scorcery. :)
I've also done some proper testing on the others and here's some interesting info:
- The 5V PSU needs to be able to supply at least 2.5A during peaks, anything below this will cause problems.
- The device never gets even warm no matter how much disk reading you do.
- The smaller device fits much better inside the CPC.
- If the PSU is not powerful enough the CPC will reset as soon as you try to access a disk, no other effects.
- Some picture darkening (as seen of the CPC6128+) will happen on the CPC if the PSU is close to it's limit, but only on CRTs, this doesn't happen on LCDs or other displays connected via an RGB to VGA/HDMI device.
One strange side effect I've found is due to something I completely overlooked: The very second that the motor starts in the drive, just happens to also be the exact moment that the CPC also needs as much power as possible. This is because almost every chip on the CPCs mainboard is being used at that exact time. Because of this, there is a sudden requirement for lots of current. Not an issue usually, but I discovered one CPC that would reset at that moment, although I was using the same PSU that didn't have this problem on other CPCs. It turned out that the electrolytic capacitor on the mainboard was bad so it couldn't handle the sudden current spike. The CPC would work fine otherwise. So if resets happen and you know your PSU is good, then there's a chance that the capacitor on the CPC is bad and you've just not known. The CPC will actually run without this capacitor in place if you have a decent sizes PSU attached, so I suspect this capacitor has been bad for a long time and IV'e never noticed.
Bryce.
Had time to finish the orders today. After testing them I'll be contacting the interested parties for postal details...
Bryce.
Look at them! Very nice! :D
Hooray!
Sent from my iPhone using Tapatalk
I like this idea but what about going the other way using 12v to provide 5v, surely a more efficient way.
Wouldn't one of those common external hard-drive power packs rated at 2A be enough?
My 6128 rating adds up to approx 15w (5V x 1.7A and 12v x 0.4A)
And you can buy small modules premade from China.
These could be used to supply 5v to external drives like goteks, 3.5 floppies etc.
I know this will upset people that like to make things themselves but for the rest of us.....
http://www.ebay.com.au/itm/1Pcs-Mp2305-Dc-Dc-Buck-Sent-Down-Converter-Module-7-20V-12V-19V-To-5V-2A-Car-I-W-/282283605224?_trksid=p2141725.m3641.l6368 (http://www.ebay.com.au/itm/1Pcs-Mp2305-Dc-Dc-Buck-Sent-Down-Converter-Module-7-20V-12V-19V-To-5V-2A-Car-I-W-/282283605224?_trksid=p2141725.m3641.l6368)
- Input voltage: DC7-20V limit 23V
- Output Current: 2A
- Work efficiency: about 92% (input 12V, output 5V1A)
- Output ripple: less than 60mV P-P
- Overload protection: protective current of about 3A
- Short circuit protection:
- Output voltage: DC5.25V + -0.05V
- Reverse Polarity Protection: None
I did consider this direction when I was designing the device, but there are a few disadvantages of going this way. The 5V rail can need a lot more than 2A quite often. The CPC is rated at 1.7A for the bare machine. Actually in reality it only pulls about 1.2A for a bare machine sitting idle, however, as you know, people now strap on extra RAM, ROM, RS232, USB Mice, WiFi, LAN, Spy Satellite Control Systems (maybe that's just me :) ) and other great stuff. 2A isn't enough for a modern CPC setup. A robust DC/DC converter that can supply 3A is a big chunky piece of hardware at least three or four times the size (and cost) of my device.
It's easier, smaller and cheaper to create a 12V 400mA (4.8W) supply from 5V than trying to create a 5V 3A (15W) supply from 12V.
Now let's take a look at the Chinese device, and a problem that people often get caught out with. The Chinese advert states the MAX figures for all values and these are the values for the IC, not for their circuit. You can not combine these: Can it supply 2A - Yes probably, Can it supply 5V - Most likely. Can it continuously supply 5V at 2A - Definitely not. You only have to look at the size of the components they've used to know that something's not right. 5V at 2A is 10W of power. Does that circuit look like it can handle 10W of power continuously? According to the datasheet, the chip can dissipate an absolute max of 1.39W. They claim that at 5V 1A it runs at 92% efficiency, so let's assume it runs at 88% efficiency at 2A (being very generous here as that's the value for 3.3V, no value for 5V in the datasheet and this assumes an ideal circuit). This means that at 5V 2A running at 88% efficiency, it would need to dissipate >1.2W, that's going to be one hot little chip with a relatively short lifespan.
External Components:
According to the datasheet, the minimum inductor current value can be calculated using the formula:
Ilp = Iload + (Vout / 2 x fs x L) x (1 - Vout / Vin) .... Let's grab the calculator.... = 2.428A
(I've chosen a 10µH Inductor, as it's the one used in the datasheet and most likely what they used)
Now check the internet for what a 2.5A 10µH Inductor looks like. It's 5 times the size of what they've used. They also chose a non-shielded inductor, so you have a very hot 340kHz transmitter inside your CPC. Now we've got and underdimensioned inductor to deal with too. This will completely invalidate their efficiency claim and the circuit will already have reached its limit somewhere slightly above 1A.
You'll also notice that they didn't even bother including the required electrolytic capacitor, just some cheap ceramic caps, so the ripple on the 12V side could and will be massive (and they conveniently don't state values for this). They also seem to have left out the bootstrap diode. So really they've just slapped together the absolute minimum required so that a voltage will come out at the other end.
There is a very good reason why this device costs $1.84... It's because that's all it's worth. I know the Chinese have drastically brought down the cost of electronics, but expecting to get a reliable 5V 2A supply from a tiny slapped together $2 PCB just isn't realistic.
Buy some for yourself, connect them up to a load and push them up to the claimed limits and do some measurements. Let me know how it goes and be careful not to burn your fingers.
Bryce.
And video it, so we can all watch the magic smoke come out and go "Oooo!" :laugh:
I guess that if I was using a 12V PSU I would make a module containing one of those good quality 5V voltage regulators, a decent heatsink and the required caps. Problem is that heat disipation would be noticeable in this case, at least pluging the 12V output directly to the regulator.
Wow, Bryce, I am humbly whipped back in to place now!
I am now really scared of all those thousands of cheap chinese 12v/5v power pak devices I have driving all my hard-drives, modems etc.
I assume they would have the same standard of circuitry in them. All ready overheat and smoke.
While you are still full of info do you know how much current a 5v Gotek drive draws?
If I do get any of those 12v to 5v circuits I will definitely video what happens.
Reminds me of the other day when I shorted out 240v AC in a power supply, now that was a bang!
When I worked as an electrician it was good to cut a live cable once with your pliers cause then you had a wire stripping hole built into them. ;D
Quote from: Bignumbas on 10:38, 18 January 17
Wow, Bryce, I am humbly whipped back in to place now!
I am now really scared of all those thousands of cheap chinese 12v/5v power pak devices I have driving all my hard-drives, modems etc.
I assume they would have the same standard of circuitry in them. All ready overheat and smoke.
While you are still full of info do you know how much current a 5v Gotek drive draws?
If I do get any of those 12v to 5v circuits I will definitely video what happens.
Reminds me of the other day when I shorted out 240v AC in a power supply, now that was a bang!
When I worked as an electrician it was good to cut a live cable once with your pliers cause then you had a wire stripping hole built into them. ;D
:D My intention wasn't to "whip you back into place", just inform.
I don't have a Gotek to test, but it's based on an ARM Cortex STM32F105 and a few external bits, so I can't image that it needs more than maybe 300mA at the very most depending on the USB stick used. To be compliant with the USB standard, the supply
should be able to provide at least 500mA + whatever the circuit needs because that's what the USB standard requires.
You don't need to be scared of those cheap power packs as long as you aren't using anywhere close to the amperage they claim, but I still wouldn't leave them turned on when I'm not home.
Bryce.
What 5V PSU's are people using for their CPC's?
Would something like the below be suitable?
https://www.lindy.co.uk/power-c8/power-accessories-c341/multi-country-switching-ac-adapter-5v-dc-2-6a-2-5mm-inner-5-5mm-outer-dc-jack-type-p7406
It seems all the ones I can find are 'switching' rather than 'linear'?
I guess that nowadays linear PSUs are used mostly for audio only :) As Bryce said, you can also buy a nicely filtered switching PSU, that is more efficient and less bulky that the linear ones. I am kind of a dinosaur in that regard and I like to use linear PSUs and CRTs with my machines from the 80s, since it is they way they were originally conceived, but I am sure that Bryce can point you to a nice switching PSU :) On the other hand, if you do not use a CRT, it is unlikely that the switching PSU will cause major problems, even if it is not perfectly filtered.
Quote from: Skunkfish on 12:01, 18 January 17
What 5V PSU's are people using for their CPC's?
Would something like the below be suitable?
https://www.lindy.co.uk/power-c8/power-accessories-c341/multi-country-switching-ac-adapter-5v-dc-2-6a-2-5mm-inner-5-5mm-outer-dc-jack-type-p7406 (https://www.lindy.co.uk/power-c8/power-accessories-c341/multi-country-switching-ac-adapter-5v-dc-2-6a-2-5mm-inner-5-5mm-outer-dc-jack-type-p7406)
It seems all the ones I can find are 'switching' rather than 'linear'?
For a bare CPC with no expansions that would be fine. Regarding the amps stated even on good PSUs: You should aim to be using slightly above 50% of its capacity, so if the device you are powering needs 2A, go for a 3.5A supply. The 2.6A stated on the PSU is the absolute maximum it can supply and you don't want your PSU to be running a max the entire time. It will get hot and die earlier than expected.
Bryce.
All devices have been tested (just one failed). So I will be sending PM's out later today.
Bryce.
Great stuff! Looking forward to getting mine.
As I'll be shipping this week, a quick note to those who are waiting for their device to arrive: The connector to the drive is deliberately mounted at a slight angle. This isn't a mistake or something that happened in the post, so don't try to bend it back to 90° :D It's meant to be like that. The PCB sits at a slight angle so that it fits inside the case. It's a very tight fit. See attached picture.
Bryce.
Hi Bryce - thanks for this information :)
Mark
That is actually a good advice! knowing my OCD I would have probably tried to desolder the connector and put it straight :picard:
To all those who ordered a 5VCPC: They will be going out in tomorrows post.
Please give some feedback when you've tried them out with details of the PSU you are using and whether the electrolytic capacitor in your CPC has ever been replaced. Also, to answer a question from one user: You can leave the 12V flylead in place if you like and even connect it to 12V when the 5VCPC is installed, it won't be taking the 12V from this connector though, the 5VCPC will still be creating the 12V.
Regarding installation: You will probably have to remove the two screws holding the drive in place to lift the drive and re-arrange the molex connector cable to the new position (other side of the flat cable). Also, be careful when putting the top of the case back on, put the case over the device and then move it forward into place. The 5VCPC can wobble a bit when the case top isn't on, but the case will hold it firmly in place when replaced.
To all those who didn't order a 5VCPC: I still have a few left if anyone is interested.
Bryce.
I will be reporting as soon as I install it, although I am planing to change all the caps and I am using a 5A PSU. I do not expect any surprise :)
Arrived today, thanks Bryce! Tiny little thing, obviously well made.
At first it didn't work for me. Then I realised the power supply I was using was too weak (2A). So I hooked it up to a PC supply with "proper 5v power" and now it's all good.
My 6128 has not been used for a long time, and it seems to be having difficulty reading disks... Including the CP/M disk :(
Oh well, back on the shelf with it. Another problem for another time... ;) ..but I will be back using it again soon (right after my current project is complete. 6128 is next in the list).
P.S. No caps were replaced during the making of this post.
I also got mine!
The device is really small and fits very well on the back of the drive. It works beautifully too!
I tried it with my CTM644 monitor because I couldn't wait to get a new psu, and everything went like a charm but for the monitor blinking when the drive motor starts. This, of course, is the result of the CTM not having enough power but, in any case, the device performed very well and the disk drive worked as expected.
With a decent psu and a scart cable, my CPC is free to go wherever I need it to!
Thank you very much!
Mine has arrived :D
Don't know when, as I have been away for a week. It was waiting for me when I got home this evening.
Although the packet it was in looked very similar to how another hobbyist who lives in Germany, does his. As I picked it up I was racking my brains thinking, I already had a parcel from him last week, what has he sent me?
But all was revealed after I opened it ;D
Thanks Bryce :D
Mark
PS, at the Stardot meet-up today, your BBC joystick adapter was the topic of one conversation.
Still waiting for mine... let´s see tomorrow :) Anyway, until next weekend (luckily) I am afraid that I will not be able to start with my project, so no rush :)
Quote from: 1024MAK on 23:00, 29 January 17
Mine has arrived :D
Don't know when, as I have been away for a week. It was waiting for me when I got home this evening.
Although the packet it was in looked very similar to how another hobbyist who lives in Germany, does his. As I picked it up I was racking my brains thinking, I already had a parcel from him last week, what has he sent me?
But all was revealed after I opened it ;D
Thanks Bryce :D
Mark
PS, at the Stardot meet-up today, your BBC joystick adapter was the topic of one conversation.
The Joystick adapter is still very popular. I've just ordered PCBs for another batch of them.
Bryce.
Can I just check that I've connected the lead correctly before I power up for the first time?
Yes, that's correct. And even if it wasn't (if you had put the white connector on the wrong way), it would not cause any damage as long as the 12V supply is no longer connected.
What type and amperage is the 5V PSU you intend using?
Bryce.
Great success! It works, the CPC boots ok even with my 2a psu and your svideo adapter attached
However the machine will reset as soon as I try and access the floppy drive. And if I attach the USB floppy emulator then it won't boot at all. So my psu is too weak. Time to order a better one!
The 2a psu is strong enough to power the CPC, svideo adapter and M4 wifi board though.
Yes, if your PSU is anywhere below about 2.6A then the current rush when accessing a disk will cause the CPC to reset. Not sure why the USB Floppy emulator stops the CPC from booting. The 5VCPC has absolutely no effect on it. Does the emulator use the 12V rail for anything? Or more important, is the power socket pinout not reversed on those emulators?? :o .
Bryce.
The USB floppy emulator takes a 5v feed, so the 5v out from your svideo adapter is split into the CPC and into the floppy emulator.
Wow, it must be pulling quite a bit of current then! That means your PSU was already running at it's limit before you installed the 5VCPC.
Bryce.
Yes, it was high on my list to replace even before I read about the 5VCPC!
Do you think this might be a suitable replacement?
genuine jentec 5v 3a right angle 5.5mm x 2.1mm router d- link power supply https://www.amazon.co.uk/dp/B00JSCTYPI/ref=cm_sw_r_cp_api_BkkKybZ4TX509
I'd probably go a bit higher (4A), as the Amp rating is usually the peak value, not what it can sustain over a longer time.
Bryce.
Ok, but 2.1mm is the correct jack size?
Quote from: Trixster on 15:48, 31 January 17
Ok, but 2.1mm is the correct jack size?
Yes, 2.1/5.5 for the Classic CPC, 2.5 for 5.5 for the Plus.
Bryce.
I've found a decent 4a psu. It works perfectly, the CPC runs fine with both the M4 and the USB floppy attached. Top little upgrade Bryce, I love it!
Actually, I've noticed that I get a better picture from the svideo adapter with this new psu, so the 2a one must definitely have been on its last legs or pushed to the limit.
Great, glad it all works fine for you. The 2A PSU was probably only good up to 1.5A which is already pushing it for a CPC on its own. When they claim 2A, that's what it can supply in short bursts and peaks, not what it can constantly supply.
Bryce.
Guess I'm late to the party. But if you choose to make more in the future I would be interested in buying two 5VCPC's. :)
Regards,
Bjørn
I think I have the parts for two still. I'll check at the weekend and send you a PM.
Bryce.
How about this for a PSU? Anyone heard of them?
https://www.amazon.co.uk/GOOD-LEAD-Adapter-Charger-5-5mmx2-1mm/dp/B01M9J8LZS/ref=sr_1_2
Quote from: JonB on 06:45, 08 June 17
How about this for a PSU? Anyone heard of them?
https://www.amazon.co.uk/GOOD-LEAD-Adapter-Charger-5-5mmx2-1mm/dp/B01M9J8LZS/ref=sr_1_2 (https://www.amazon.co.uk/GOOD-LEAD-Adapter-Charger-5-5mmx2-1mm/dp/B01M9J8LZS/ref=sr_1_2)
The company rebadges PSUs, but it looks like they test and stand behind their products. They are in Belfast, so if anything did go wrong, you have someone to go to: https://acadaptershop.co.uk/about-store (https://acadaptershop.co.uk/about-store)
The PSU itself looks to be pretty high quality.
Bryce.
OK, I ordered it. Now I can get rid of that cheapo 12v/5v PSU.
Thanks Bryce!
Here is what I did (http://amstradplus.forumforever.com/t309-C-ble-alimentation.htm).
Please takes notes that i made this cable for free :P