Plan: To build a load tester capable of testing computer power supplies, CPU VRMs and other various power circuits.
Specifications:
* 0 - 50V source voltage (55V surge) (Not reverse polarity protected)
* 0 - 100A current (100A at >0.8V)
* 0 - 500W dissipation (up to 1kW for 10 seconds)
It will be based on an old amplifier case which I have recovered from an amplifier I found in a skip. The amplifier has a large heatsink. The unit will be air cooled, or maybe even water cooled, if I can work that out.
Hardware plan:
* 2 x 0.01 ohm (paralled) 100W current shunt resistors attached to the main heatsink. Both devices dissipate 25W each at 100A, so they are operated well within ratings.
* 150A automotive fuse (rated to 63V.)
* 18 x IRFZ44VZPBF mounted on the heatsink, evenly spaced, with mica pad and thermal paste. Each fet dissipates ~28W at full load.
* Kelvin current sensing across each shunt resistor (individually summed.)
* Kelvin voltage sensing optional; by default sensed near the main terminals.
* 16x2 LCD.
* Optical encoders for setting parameters.
Software plan:
* PIC controlled (dsPIC or PIC18.)
* Can set constant current, constant power and constant resistance.
* Can view voltage, current, power, simulated resistance and temperature.
* Support for transient and varying loads (for testing transient response) as well as fixed configurations.
TODOs:
* Figure out what type of wire used to route 100A through the device. I have a lot of wire removed from computer power supplies. It's AWG18. This can carry about 14A per wire. So I was thinking of paralleling a lot of these wires (x10 each way) together to route the internal high power bus.
* Figure out how to fit the fuse - for now it's going to be soldered in, but it would be better to have a fuse holder in case the fuse blows.
* Figure out how well the amplifier's heatsink will work with air cooling, and if it will be good enough for 500W (I think it will be.)
* Design the main control board.
* Think about the best connector for the power terminals. Initially I will just loop a lot of AWG18 and maybe use some kind of adhesive or solder to keep it together... However maybe some kind of high current banana plugs would work better?
I've already got the power shunt resistors and thermal paste, and more components are on their way.
Specifications:
* 0 - 50V source voltage (55V surge) (Not reverse polarity protected)
* 0 - 100A current (100A at >0.8V)
* 0 - 500W dissipation (up to 1kW for 10 seconds)
It will be based on an old amplifier case which I have recovered from an amplifier I found in a skip. The amplifier has a large heatsink. The unit will be air cooled, or maybe even water cooled, if I can work that out.
Hardware plan:
* 2 x 0.01 ohm (paralled) 100W current shunt resistors attached to the main heatsink. Both devices dissipate 25W each at 100A, so they are operated well within ratings.
* 150A automotive fuse (rated to 63V.)
* 18 x IRFZ44VZPBF mounted on the heatsink, evenly spaced, with mica pad and thermal paste. Each fet dissipates ~28W at full load.
* Kelvin current sensing across each shunt resistor (individually summed.)
* Kelvin voltage sensing optional; by default sensed near the main terminals.
* 16x2 LCD.
* Optical encoders for setting parameters.
Software plan:
* PIC controlled (dsPIC or PIC18.)
* Can set constant current, constant power and constant resistance.
* Can view voltage, current, power, simulated resistance and temperature.
* Support for transient and varying loads (for testing transient response) as well as fixed configurations.
TODOs:
* Figure out what type of wire used to route 100A through the device. I have a lot of wire removed from computer power supplies. It's AWG18. This can carry about 14A per wire. So I was thinking of paralleling a lot of these wires (x10 each way) together to route the internal high power bus.
* Figure out how to fit the fuse - for now it's going to be soldered in, but it would be better to have a fuse holder in case the fuse blows.
* Figure out how well the amplifier's heatsink will work with air cooling, and if it will be good enough for 500W (I think it will be.)
* Design the main control board.
* Think about the best connector for the power terminals. Initially I will just loop a lot of AWG18 and maybe use some kind of adhesive or solder to keep it together... However maybe some kind of high current banana plugs would work better?
I've already got the power shunt resistors and thermal paste, and more components are on their way.
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