Electronics > Beginners

Electronic Load

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requim:
I've been acquiring power supplies.  Apparently it's become my thing.  Working or broken, as long as it's used I've been looking at them.  Anyway, I've been looking at electronic load devices and I wanted to know more about them.  The primary reason why I'm looking at them is because I want to test the loads, and I'm not really sure how else to do it.  I know I can measure current and amperage off of them with a multimeter, but I'm assuming an electronic load device is used to pull a steady load off the device as a burn in tool or something.  Is that right?  Is there more to them than that? The one thing I do know about them is that they appear to be pretty pricey!

Any suggestions on a good one?

alm:
Dave made a video about how to build a dummy load, this may be helpful. Your DMM in current mode represents almost a direct short and dissipate almost no power, a dummy load will dissipate the power. It can either be constant or sometimes modulated (to test transient response/stability). The current and/or voltage it draws is often variable.

hacklordsniper:
For arround 300-400 $ you can buy a programable dummy load (300 V, 30 A, ~180 Wmax), soon i will recieve one from iTech and do a review.

requim:
I wouldn't mind going the DIY route.  I watched Dave's video and if his design could be modified to handle 4 amps or so from 0 - 35 volts that should handle everything I want to test for now.  Has anybody built one spec'd similiarly or has anyone seen a good schematic for one??

Balaur:

--- Quote from: requim on November 01, 2011, 04:21:22 am ---I wouldn't mind going the DIY route.  I watched Dave's video and if his design could be modified to handle 4 amps or so from 0 - 35 volts that should handle everything I want to test for now.  Has anybody built one spec'd similiarly or has anyone seen a good schematic for one??

--- End quote ---

I've built something like this at some point and I've still have it around. Mine draws up to 3 and something amps and dissipates safely about 100W.

There are some tricky stuff you may want to be aware of:
- you need an opamp that's not afraid to drive capacitive loads
- and a transistor with a low input capacitance
- but your design may still oscillate at some operating point.
- it's better to have a transistor with a low Vgs(th) - logic level FETs

Cheers,
Dan

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