I plan to control a bunch of O22 switches remotely via a microcontroller.

I would appreciate someone sharing the estimated current for the coil during the switch operation.  I know it is only momentary during the shorting of the pin to ground but I don’t want to overload the optoisolater, SSR, or relay.

I dis search but everthing I found was related to the lights.

Unfortunately  I am away from home so I cant just set one up and measure it.

Thanks,

Bill

Original Post

Rob,

I assume you meant Amps?

Thanks for the quick response.
Bill

@EastBay posted:

Rob,

I assume you meant Amps?

Thanks for the quick response.
Bill

He gave you the data he knew- the resistance of the coils typically.

Figure 5-7 ohms nominally.

The expectation then is, you knew to use Ohm's law to "do the math" to derive the current.

I is the Current in Amps, V is the source Voltage, R is the Resistance- If you know any 2 of these pieces of data, you can find the 3rd.

Divide source voltage by the above assumed resistance = approximate current value your circuit needs to be capable of.

Since we do not know your source voltage, again, he gave you the one value he knew from experience and measurements.

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Last edited by Vernon Barry

Again, let's use 14V as the source.

14V, divided by worst case 5 Ohms = 2.8 A

14V, divided by 7 Ohms = 2 A

If your source voltage is higher, then the current would be higher, less voltage, slightly less current.

Yes thank you to all for clarifying.

getting old I guess.  Lol

Rob my apologies.

You answered the question I should have asked, as resistance is the only constant here.

I guess I suffered from expectation bias in this case.

I’ll go back to copying the mail.

Bill

@EastBay posted:

Rob my apologies.

None necessary, I just assumed you had the other variables locked down as this is an interesting, advanced project.

A few years back I measured one powered by a robust 16VDC power supply on the layout, and it was peak about 3 amps, for only an instant. That jives pretty well with the calculated values above.

Rod

Figure 5-7 ohms nominally.

I find as they age the ohms goes up, I use 10 as the easy number this way you are always in the ballpark. But yes 5-7 is exact.

Thanks Rod and ThatGuy.