Adjustable Dual Polarity Power Supply

Hi Flemming,

What are your current resources. Do you have a source of parts. To build a dual bench supply you will need a transformer or two, some way to rectify the AC from the transformers secondary, a filter capacitor to smooth out the rectified current and then you will need a circuit to control the voltage and current to your outputs. Finally  you will need the extra touches such as  a case, Volt and Amp meters, power switch, power indicator, and output jacks. Building a power supply from parts and available kits and circuits can be fun and rewarding. Start putting your concept together on paper and then begin to collect parts and solve problems until you have built what you want.

John

Thank you for the reply.

I am ahead of you

I got a 2*15 V, 0.5 Amp. ring transformer, 1 amp. rectifier bridges and large capacitors ( might be too big ), the case would be part of a 3 unit high 19" rack case from Shcroff

so must of the exterior is sorted

Volt and amp. meters is necessary, not sure what i use, depend on the space on the front panel.

The concept is just about planned, even a multi funktion power indicator.

I have been looking around at other homemade power supply, one thing is a puzzle to me, why do you all use small knobs for your adjustment, it's much easier to control with a BIG knob.

The most important part is missing -the regulator circuit

Thank you for the reply.

I am ahead of you

I got a 2*15 V, 0.5 Amp. ring transformer, 1 amp. rectifier bridges and large capacitors ( might be too big ), the case would be part of a 3 unit high 19" rack case from Shcroff

so must of the exterior is sorted

Volt and amp. meters is necessary, not sure what i use, depend on the space on the front panel.

The concept is just about planned, even a multi funktion power indicator.

I have been looking around at other homemade power supply, one thing is a puzzle to me, why do you all use small knobs for your adjustment, it's much easier to control with a BIG knob.

The most important part is missing -the regulator circuit

Hi Flemming,

When I want better control I use a 10 turn pot. Most of the time I use smaller controls as that is what fits on my panels and looks good. If you haven't already looked at it here is a link to the last dual bench supply that I built. I used salvage parts and case and my net cost for this unit was about $35. US.

https://www.element14.com/community/people/jw0752/blog/2017/02/11/oh-no-not-another-power-supply

I have built one more dual supply since this one and for a cool modification I used a MOSFET controller and MOSFETs to rectify the AC instead of diodes. This gave me about 2 more volts output and cut the energy usually lost in the diode drops.

https://www.element14.com/community/people/jw0752/blog/2017/03/03/incorporating-the-lt-4320-ideal-bridge-in-the-linear-bench-supply

Take a look at the power supply board that I am using. It comes as a kit for about $7.00 from Banggood. You have to provide a proper heat sink for the output transistor but when properly heat sunk it will handle 3 Amps. I also has current limiting and zero voltage adjustment. As I mentioned I will often use a ten turn pot on the voltage control. I usually leave the current control stock as this isn't as critical.

John