 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Electronics : Power Supply Upgrade.
  Page 3 of 4   |
|||||
| Author | Message | ||||
Revlac Guru  Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
That ST data sheet is different from the NEC data sheet? Cheers Aaron Off The Grid |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes, other data sheets have the pins going the normal way with one on the left, and three on the right. http://www.alldatasheet.com/datasheet-pdf/pdf/77279/NEC/2SD882.html  Cheers, Tony. |
||||
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I believe this is the original design of these power supplies. One thing to note is it will not work off of a DC power supply it needs a negative bias provided by the AC input. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Great find Gary, thanks for that. And a neater drawing too  .I did wonder about the odd negative supply rail method, have to read through the whole article later, it looks like a good write up. Mine is 99% finished, still waiting for the digital Volt/Amp meter to arrive as this requires a hole being cut into the case. I used the largest diecast box to fit it in with the entire top surfaced with a whopping heat sink (cut down from an old computer power supply) The tranny is a 24V 160VA toroid, probably have to reduce the voltage a little, its at 31V no load with a capacitor. Klaus |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Great sleuthing there Gary. It seems that the Chinese pinched that circuit, which does not surprise me in the least. That writeup, schematic, and parts list makes a very welcome addition to the file. Anyhow, it seems to be a very sound and well thought out design and it certainly works as well as any of the commercial linear supplies I have used. The text also clears up the mystery about what the multiturn trimpot is supposed to do, although on my supplies it does not seem to have any noticeable effect. The original design specifies different op amps. I don't know if that has anything to do with it, its not something I have really looked into at this stage. Klaus, That toroid should be o/k. For others here, one point to be aware of though, if the incoming dc gets much over 35v it might be really pushing the maximum voltage rating of the op amps. Using a mosfet instead of a bipolar will also limit the maximum output voltage to the input voltage minus the gate threshold voltage, a problem you don't get with a bipolar transistor. So the whole transformer voltage issue is fairly critical. Too much or too little and it may cause some difficulties. I still need three more boxes and transformers, but the two supplies that are already built are working great, very pleased with them. Cheers, Tony. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Just looked into the trimpot issue. One supply did indeed adjust right down to zero output volts with the trimpot. The trimpot in my second supply did nothing. It was a faulty pot. Cheers, Tony. |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I did have plans to run this off DC but as I found out that does not work. So got a microwave transformer that I had rewound the secondary for doing inverter testing. It had been wound for 26V, just took one turn off so now it is 24.5VAC. I have 2 1.6 mm windings on it, so should have bo trouble run 2 variable supplies in the one box. Connected it and the PSU PCB works as it should. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It would give you much more flexibility to use two separate transformers, or at least have two 24v windings on the same transformer. The reason being that one day you might want to connect the two supplies so you can have +12v and -12v for example. You cannot do that if both are fed off the same winding, they need to be completely isolated from each other. Cheers, Tony. |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
There are 2 X 1.6 windings I was planning to separate them anyway. It is not difficult to do the rewind and much cheaper than $37 from Jaycar for a single transformer. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That will work fine. I agree $37 for a transformer and $35 for a plastic box is pretty spendy, but it does make a nice piece of gear that should last a very long time. Cheers, Tony. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Interesting to read in the original article that madness found is that using 5V6 instead of 5V1 zener diodes. That raises the reference voltage to 11.2V. Perhaps that also makes it less critical with the 30V input? The article mentions 33V somewhere. From the feedback to that article it seems worthwhile to double the primary capacitor to reduce high load ripple. I will be squeezing in another 3300uF/50V cap. Klaus |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The zeners in the kit are unmarked and probably cheap out of spec rejects. I only assumed they were 5.1v zeners, as that is what I was measuring. The second kit had one zener about 5.1v and the other much higher about 5.6v from memory. I used the 5.1v as the reference and the 5.6v to regulate the negative supply. How is it going Klaus, fired it up yet ? Cheers, Tony. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
No, not yet, still waiting for that digital display module. As this involved metalwork with fitting it I have not yet hooked up the parts. I usually finish a project first before firing it up, its way more satisfying then to see the smoke come out  Klaus |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Jeez, you are a real Masochist, complete the project and then turn it to see the smoke. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Mad,, my projects rarely smoke  , the exception was that big inverter.Its just the way I work, finish it completely, turn it on, it works - good, it does not work - put it aside and think why not, then fix it. Simple Klaus |
||||
disco4now Guru Joined: 18/12/2014 Location: AustraliaPosts: 897 |
Hi Warpspeed, I like your mounting idea for the mosfet. The screw terminal you are using here looks like the pins through the board and where the wire (mosfet legs) connect in are in the same direction i.e both vertical , with the screws coming in at 90 degrees. I can't seem to find any like that, do you have a source for them. Regards Gerry Latest F4 Latest H7 |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Gerry, Altronics sells them. You can get 45 degree entry as well. just make sure the terminal spacing suits the Mosfet leg spacing. Klaus |
||||
| disco4now Guru Joined: 18/12/2014 Location: AustraliaPosts: 897 |
Thanks. Latest F4 Latest H7 |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Klaus has nailed it. Altronics P-2065A (ninety degree three way) Cheers, Tony. |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You can buy those connectors for 27 cents each but the catch is only in lots of 100 here. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Page 3 of 4 |
|||||
 Print this page |
