While disassembling a little electric oven (rated for 1300W at 230V), I scavenged one of the heating elements inside, which I measured its resistance to be about 40 Ohms (let's call it
Since it should be able to handle some power, I would like to use it as a "mild" load, for testing power supplies. For instance, let's say I have a 5V DC, 550 mA power supply (let's call it
Ptest): once connected,
Rload should draw around 125 mA, loading
Ptest a bit.
I have a Rockseed RS310P programmable power supply, on which I can set voltage and current up to 30V and 10A (let's call it
Pvar). I thought about connecting
Ptest in series with
Rload, like this:
My idea is that, by setting the current limit of
Pvar, the PSU will act as a constant current source and it will adjust its voltage to whatever is needed to mantain that current. The current will cause a certain voltage drop (
Vload) at the load, and given that
Vload must be equal to
Vtest + Vvar,
Pvar will adjust its voltage to be
Vvar = Vload - Vtest.
For instance, given the current limit
Iset = 250 mA,
Vload = Iset * Rload = 10V,
Vvar = Vload - Vtest = 5V: in order for 250 mA to flow through
Vvar must be 5V. But, since everything is connected in series, this means that 250 mA are flowing through
Ptest aswell, which is the effect I'm interested about: from
Ptest point of view, it should be like a load which is drawing 250 mA.
Thus, setting the current limit could drive this makeshift "variable load" within a certain range: in this case, I should be able to go from a little above 125 mA up to 875 mA (by setting
Vvar to 30 V, which means
Vload = Vtest + Vvar = 35 V.
I know proper variable loads exist, but I would like to know if this could really work: theoretically it should, although I don't know much about power supply topologies (except really simple unregulated ones) so I'm not sure about practical pitfalls or even safety hazards involved.
How about connecting a battery instead of a power supply as test source? It should discharge the battery at a specific current.