Symmetric Power Supply 0-70V @ 5A
I want to build a new symmetrical power supply with the following demands:
-PC controlled via USB
-The set value and the actual value of the voltage and current can be read on lcd displays.
My order of transformers at pollin:
The start of the build (I mounted the transformers on a piece of treaded rod and mounted it on a angle bracket)
I got another order today. This time from Reichelt.
-5 MJ2955 Transistors
-8 Relays 12V 10A
-8 resistors 0.1 Ohm 5W.
-Spacers to mount the pcb's
I mounted the resistors and transistors on the heat sink:
This update is not from today but from the past year. I have done a couple of small changes and didn't post them on the site at that time. Now it is time to finily do that.
The first change was that I mounted the transformers in the other direction. This way I'm saving space and I have wound some extra coils at 2 transformers to power the logic.
A picture of how the power supply looks like at the moment
I also decided that I'm going to use rotary encoders instead of toucht ic's. Therefore I ordered some rotary encoders at Sure Electronics. I'm going to use 4 of them in this power supply.
I bought some bigger heat sink for cheap. (Thanks Ben and Robert). I have put those new heat sinks on this power supply. With this heat sink it doesn't need a fan, because the ribs run in the other direction and the heat sink is much bigger. I cut 5cm of the case at the back and mounted the heat sinks. In the middle I've put a panel for the power connector and in the future a usb connector.
I also made a new switch pcb because I was not happy anymore with the old design. The triacs to switch the 230V side of the transformers are driven by an PIC12F629. I have put a low power powersupply on this pcb to generate 2*5V from the extra windings I made around the transformers.
R1, R2, R3 220R R4, R11 33K R6 0R33 5W R5 3K3 R7, R8, R9, R10 1K C1 470µF 25V C2 100nF C3, C4 10µF 25V C5, C6 1000µF 25V C7, C8, C9, C10 100nF SMD 0805 D1 1N4007 D2 5V1 D3, D4, D5, D6 1N4007 SMD B1, B2 rectifier IC1 PIC12F629 (Code) (Hex) IC2 7812 IC3 7912 K1, K2, K3, K4 Relays LED1 LED 5MM red Q1, Q2, Q3, Q4 BC848 SMD T1, T2, T3 TIC206D
After a long time I restarted building on this power supply. I found a circuit where I'm going to base it on.
I'm not going to use this circuit exactly, but the main part I do.
In this design they used TIP142 transistors. In my version I used MJ2955 transistors. I was doubting if I would change the design or change the transistors on the heat sink. After a lot of thinking I opted for the second option. The new transistors are mounted directly on the heat sink, where the old ones used an bracket. This should provide a better cooling.
I didn't trust the big capacitors I first planned to use anymore. 1 of the 2 is so dehydrated that if you shake it you hear the inners rumbling louse. Instead of buying new big capacitors I opted to buy a few smaller ones. This is cheaper and gives a lower ESR. To mount them I made a pcb. Per side I use 3 capacitors of 3300µF 100V. That gives a capacity of 9900µF per side, this should be more than enough.
The next update will be the analog print. This design is 90% ready so it should not take too long (if no other project gets in between.)