Parallel prox switches.

[ptonsparky]

I haven’t tried it and only have one DC prox switch on the shelf, will they work in parallel?
They would operate a small interposing relay.

 

[__dan]

Don't know. There is a small off state leakage current for the transistorized output, which would be doubled, but likely not enough to pull in the coil.

Prox is usually an input signal device, not an output or load driving device. If the prox transistor output is rated for the load and the coil switching transient is properly suppressed, it may work.

 

[ptonsparky]

FWIW, they are 2 wire.

 

[Jraef]

What do you mean by "in parallel"? Like an "AND" logic circuit? Are the proxes going into a PLC and you're just trying to eliminate one input? Wouldn't be worth the risk compared to just doing it in logic. If going to a relay, it might work because of the impedance of the relay coil.

 

[__dan]

The two wire device is self powering by using the neutral at the other side of the load, through the load. Probably has a higher off state leakage current than a three wire device, which would be doubled in parallel. This self-power requirement is still very low since it not trying to do something more ambitious, like charge the buffer battery, run a small cpu, and wifi.

The original gen 1 Nest thermostats were two wire devices that would self power through the load, but they would make the Honeywell boiler control sound like a doorbell buzzer from the load coils pulling in and out.

 

[ptonsparky]

What do you mean by "in parallel"? Like an "AND" logic circuit? Are the proxes going into a PLC and you're just trying to eliminate one input? Wouldn't be worth the risk compared to just doing it in logic. If going to a relay, it might work because of the impedance of the relay coil.

“OR”.

Either one or both.

 

[gar]

171110-1056 EST

Whether two parallel contacts perform logical OR or AND depends upon whether you are working with positive or negative logic.

Most people normally work and think in a positive logic mode. So for them parallel contacts are an OR function.

Consider cascading three NAND gates. Assume the first is performing the AND function, the next is an OR function, and the third is back to an AND function.

Can you parallel two two wire prox switches? This will depend upon on the characteristics of the prox switches, the power source, and the load.

A two wire prox switch derives power for its operation from the current thru the prox. This means there must current thru the prox whatever the output state of the prox is. Probably this means there must be reasonable voltage drop across the prox when in its closed state.

Do some measurements on a single prox to see how it works works, then with two parallel proxs.

Report results.

 

[ptonsparky]

171110-1056 EST

Whether two parallel contacts perform logical OR or AND depends upon whether you are working with positive or negative logic.

Most people normally work and think in a positive logic mode. So for them parallel contacts are an OR function.

Consider cascading three NAND gates. Assume the first is performing the AND function, the next is an OR function, and the third is back to an AND function.

Can you parallel two two wire prox switches? This will depend upon on the characteristics of the prox switches, the power source, and the load.

A two wire prox switch derives power for its operation from the current thru the prox. This means there must current thru the prox whatever the output state of the prox is. Probably this means there must be reasonable voltage drop across the prox when in its closed state.

Do some measurements on a single prox to see how it works works, then with two parallel proxs.

Report results.

My original intent was to use a small Ice Cube relay but found a DC multifunction timer with a small indicating LED. That LED glows when the prox is connected, turns a bit brighter when a target is passed in front of the prox, then full bright after the delay has elapsed on the timer. The LED on the prox changes levels as the timer changes states as well. Showing what we expected even without a meter. I will play with two proxs if we get the project but considering how low the costs are for sensors and small AB HUH relays, I won't sell them paralleled. Fifteen minutes on the road to "fix" things would more than negate any savings.