On 2007-12-17, Grant Erwin wrote:
There is an idle solenoid mounted on the side of the carburetor. When it is
energized, it pulls the governor arm to an idle position. When it is
de-energized, it releases the governor so it goes to the weld position.

This idle solenoid has a coil resistance of 5.6 ohms, so run from 12V will
draw about 2 amps DC.

This is what I want to control. The power I have available to switch on or
off to a relay coil is just 12VDC, basically a car battery.

This is a gas engine coupled to a welder, a relatively crude machine.

Azotic already posted that my relay won't work to switch a DC load. Now I'm
trying to find one that will, hopefully that won't break the bank.

Coil voltage: 12VDC
Load voltage: 12VDC

Hmm ... does the generator part produce AC? If so, you could
run that through a transformer to produce 12VAC, through the SSR, and
into a bridge rectifier and capacitor so you would have AC to switch
with the SSR. If it only produces DC, your choices would be a real
relay with a coil (lots are available in 12V versions) or a circuit
using a transistor, and a diode across the solenoid's coil to suppress
the high voltage spikes produced when the circuit turns off.

I, personally, would go for the physical relay with a coil as
the simpler device. Good ones, properly sized for the load, will last
through more cycles than the rest of the mechanism of the welder will be
likely to survive -- even from new.

SSRs are a poor choice for this task, I think. They require
additional complication of the whole setup.

Good Luck,
DoN.

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