High Current Test Load for Dummies

I saw a couple of older threads that gave me some cool ideas. I wanted to post in that thread, but then I thought about the age of the thread (btw, how old is to old?) and thought I would get crucified if I did :eg: Anyhow, I'm looking at educating myself so that I can eventually make some high current test loads. It makes sense that the longer it runs the hotter it gets, so how about heat-sinking the test load??? And how can we get the test load up to 5 Amps and also make it adjustable so there can be one test load that will do it all??? I saw the threads that you guys built the selectable 3 Amp test-load and wanted to make a nasty circuit that could handle the heat and be adjustable all the way up to 5 Amps.... Is this even possible??? And is there a way to make the selection without using the jumpers, are there other types of switches that will work???

I did hours of reading the different threads so please don't think I'm asking a question without reading, it was all the reading that caused the questions :beer:

Just pop a few 5A rectifier diodes in series and away you go If you want it to be selectable you can also use some 5A toggle switches instead of jumpers.

I would use an ammeter rather than a 1ohm resistor for simplicity.

ARG said:

Just pop a few 5A rectifier diodes in series and away you go If you want it to be selectable you can also use some 5A toggle switches instead of jumpers.

I would use an ammeter rather than a 1ohm resistor for simplicity.

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Thanks ARG, this project has been on my mind a lot lately...

Can you clarify the second part? Are you talking about integrating one of these into the circuit: Slim DC 0-9.99A Red/Blue/Yellow/Green LED Digital Ammeter 0.36 DC Current Monitor Meter for Motorcycle Car and DIY ect???

I appreciate you helping me out, :thanks:

Yes, but you will need an external power source (like a 9v battery) and a current shunt. If you have a multimeter just set it to Amp mode and put the test leads in series with the test load. Its easier this way.

Fleebay has a few 5Ampers but they only come in 40V, 60V, and a 100V... If the 1N4001 is rated up to 1A/50V, does it matter for this specific project if the voltage rating drops to 40V or even goes up to 100V?

J0SHUA said:

Fleebay has a few 5Ampers but they only come in 40V, 60V, and a 100V...

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I don't quite understand what you are trying to say.

If the 1N4001 is rated up to 1A/50V, does it matter for this specific project if the voltage rating drops to 40V or even goes up to 100V?

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The 1N400x series is rated for a maximum of 1 amp. The last digit denotes the maximum forward voltage the diode can withstand.

Zeebit said:

I don't quite understand what you are trying to say

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I'm just not sure what 5A diode is the best to use... my question was in regard to the different voltages each of those diodes are rated. If the 1A test load has a rectifier diode that is rated 1A/50V, what should the 5A diode be rated? Should I be looking for a 5A/50V?

Does it even matter what the VRRM or VRWM is???

I apologize, for I have a lot to learn...

The reverse voltage doesn't matter. your only concern is the forward voltage drop and the maximum forward current of the diode.

J0SHUA said:

If the 1A test load has a rectifier diode that is rated 1A/50V, what should the 5A diode be rated? Should I be looking for a 5A/50V?

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The voltage rating does not matter since diodes are only operating at less than 10V. You could even use the ones rated up to >500V.

djQUAN said:

The reverse voltage doesn't matter. your only concern is the forward voltage drop and the maximum forward current of the diode.

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Thanks djQUAN!

Zeebit said:

The voltage rating does not matter since diodes are only operating at less than 10V. You could even use the ones rated up to >500V.

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That's kinda what I was thinking but I wanted to be 100% positive.

What about operating temperature? There was a diode the said it was rated at +175 C! and then there was a different one that gave a range between - 65 C to + 150 C?

Are there better choices other than these: Schottky Diodes & Rectifiers | Mouser?

I'm just trying to think ahead, and if there is 5A running through this thing I can only imagine that it will heat up, so I was thinking that maybe some of these diodes are better than others, at least for this job anyways...

You want regular silicon diodes. Schottky diodes have a lower forward voltage drop so you'll need more in series to get the same voltage drop as a laser diode.