Electronics > Beginners

Standard electric kettle as a DC dummy load ?

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mtdoc:

--- Quote from: Shock on July 13, 2018, 04:27:20 pm ---
--- Quote from: mtdoc on July 13, 2018, 03:55:50 pm ---Cheap water heater elements can be used for a dummy load but even they have a high enough resistance (the one I have is 8 ohms) that many in parallel would be needed to fully test a 1200W 12V supply.

--- End quote ---

Do you have a part number for your 8 ohm one? Is it a constant resistance?

--- End quote ---

No part number. It's a cheap one I picked up a a local plumbing store. It's stamped 8 ohms. And that's about what I've measured it to be at room temp. I've not tested it further.

Kalvin:
How about some thick wire or beefy resistor(s) submerged into mineral oil? Probably requires a pump to keep the oil moving and transferring the heat from the wire/resistor(s).

SeanB:
Does not really need a pump, the oil or water will convect naturally. Just keep the hot surface of the resistor off of the plastic walls and it will be fine.

I did make a few quick and dirty dummy loads using a regular cup of cold water, a sacrificial TO3 power transistor ( I used 2N3773's that had survived the detonation of the UPS units they were part of), some wire and a resistance decade box to supply base current to them. They would run fine, boiling the water, till it was below the device, so just had to have some extra water handy for long load testing. Solder to base and emitter, a M4 nut and bolt to connect the collector, or just solder the wire to the top of the steel can. Worked from 1A to 15A, up to 100W of power dissipation.

CopperCone:
I highly recommend that you make a spacious box made of steel mesh to house any kind of loads like this.

I have seen dummy loads like this meant for this using light bulbs, they put the bulbs in a steel mesh box basically to eliminate risk of electrocution and burns. This was meant for either parallel or series light bulbs with the circuits. Also stores nicely and looks good and protects it from falling screw drivers and other things.

Having blazing hot light bulbs, heat sinks, wire in the open is asking for trouble and possibly fire.

Home depot sells material that would work well.
https://www.homedepot.com/b/Hardware-Metal-Sheets-Rods-Sheet/N-5yc1vZc27v


If you use oil as a coolant and it gets real hot I would recommend you weight the platform down with some lead or stone and add some kind of splash guards (i.e. make baffles), and if it is not meant to get hot you should put a thermostat on it to break the circuit if it shorts out and starts to over heat so you don't accidentally deep fry yourself. A drain valve on the bottom would be nice to if you make some kind of oil testing tank so it can be stored drained.

Shock:
One idea is connecting up a 12V mains inverter and sticking the load on the inverter. No idea how accurate that would be but you could really punish a 12V DC supply that way if you wanted to.

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