A homebrew power supply

**anickode** · 08-17-2013, 08:08 PM

Well, it's finished, and all wired up. Did some load testing on it today, and the results are satisfactory, considering I didn't spend a dime on it. Everything was out of my parts bins. The voltage drop under load was very consistent up to 400 watts of resistive load.

OCV: 15.5v (I added one more turn on the secondaries from the original configuration)
100w load 14.6v
200w load 13.8v
300w load 12.9v
400w load 12.1v
500w load seems to have over-saturated the transformer and it dropped to 10.1v This was a 700w microwave transformer with already low efficiency, so considering it's now poorly wound with THHN, I'm not disappointed with the results.

I added a 120 ohm 5w resistor across the capacitor to bleed it down. 15v isn't much of a safety risk in terms of electrocution, but a 1 farad capacitor holds a hell of a lot of juice... 1 farad = 1 ampere/second per volt... do the math that's 750 amps for 20 milliseconds, which is more than enough to do some damage if inadvertently discharged through something sensitive. I'm hoping the large capacitor will help support the voltage under surge loads.

**the caveman** · 08-17-2013, 09:20 PM

Originally Posted by anickode

Well, it's finished, and all wired up. Did some load testing on it today, and the results are satisfactory, considering I didn't spend a dime on it. Everything was out of my parts bins. The voltage drop under load was very consistent up to 400 watts of resistive load.

OCV: 15.5v (I added one more turn on the secondaries from the original configuration)
100w load 14.6v
200w load 13.8v
300w load 12.9v
400w load 12.1v
500w load seems to have over-saturated the transformer and it dropped to 10.1v This was a 700w microwave transformer with already low efficiency, so considering it's now poorly wound with THHN, I'm not disappointed with the results.

I added a 120 ohm 5w resistor across the capacitor to bleed it down. 15v isn't much of a safety risk in terms of electrocution, but a 1 farad capacitor holds a hell of a lot of juice... 1 farad = 1 ampere/second per volt... do the math that's 750 amps for 20 milliseconds, which is more than enough to do some damage if inadvertently discharged through something sensitive. I'm hoping the large capacitor will help support the voltage under surge loads.

Nice! Is it getting painted and maybe your own decal design? I have a guy close by that can do any decal design you want or custom decal solutions for a small price. Pm me if your interested.

**Fogdog** · 08-20-2013, 03:37 PM

Originally Posted by anickode

Well, it's finished, and all wired up. Did some load testing on it today, and the results are satisfactory, considering I didn't spend a dime on it. Everything was out of my parts bins. The voltage drop under load was very consistent up to 400 watts of resistive load.

OCV: 15.5v (I added one more turn on the secondaries from the original configuration)
100w load 14.6v

200w load 13.8v
300w load 12.9v
400w load 12.1v
500w load seems to have over-saturated the transformer and it dropped to 10.1v This was a 700w microwave transformer with already low efficiency, so considering it's now poorly wound with THHN, I'm not disappointed with the results.

I added a 120 ohm 5w resistor across the capacitor to bleed it down. 15v isn't much of a safety risk in terms of electrocution, but a 1 farad capacitor holds a hell of a lot of juice... 1 farad = 1 ampere/second per volt... do the math that's 750 amps for 20 milliseconds, which is more than enough to do some damage if inadvertently discharged through something sensitive. I'm hoping the large capacitor will help support the voltage under surge loads.

Man, that is sweet. Totally awesome Bro.