How can I monitor the status of a mechanical switch in a Bowling Machine controll.

MisterBill2

Joined Jan 23, 2018
18,167
OK, the circuit that I described in post#8 can still show when the contacts are open, and since the PR2 contacts would confuse things it will not matter because those only close when the PR4 contacts are closed. So that circuit will work if the low current relay supply is completely isolated. And it could even be AC, but it must be much to low a voltage to operate that PR2 coil device. normal mains frequency will be fine, or use DC.
 

MisterBill2

Joined Jan 23, 2018
18,167
REally, the resistance of that solenoid does not matter because when it is energised the switch contacts will be closed and thus the voltage applied to the monitor circuit will be not very much. and if the connection polarity is correct, when the switch is open no current will be flowing in the monitor circuit. So really, none of that matters IF the 5 volts monitor part is indeed isolated and the polarity is correct.
 

sghioto

Joined Dec 31, 2017
5,376
Now that I have seen the rest of the circuit (accurately described by Charlton Heston in the original Planet of the Apes " It's a madhouse!") IMHO I believe the best solution is this SSR circuit using a CPC1018 as suggested by KeepItSimpleStupid.
It's operation is solely dependent on the opening and closing of SW4 with complete isolation from the 5 volt logic.
1617391089789.png
 

MisterBill2

Joined Jan 23, 2018
18,167
Now that I have seen the rest of the circuit (accurately described by Charlton Heston in the original Planet of the Apes " It's a madhouse!") IMHO I believe the best solution is this SSR circuit using a CPC1018 as suggested by KeepItSimpleStupid.
It's operation is solely dependent on the opening and closing of SW4 with complete isolation from the 5 volt logic.
View attachment 234313
Is that unmarked common (ground) connection actually available?If not then the R2 is not able to supply bias voltage. The same circuit with an isolated 5 volt supply but no R2 is a solid state version of what I have suggested twice.
 

MisterBill2

Joined Jan 23, 2018
18,167
Not if you mean a separate 5 volt supply not connected with the logic circuit.
View attachment 234317
YES, that is the whole concept of isolated. Except in series with the switch contacts,(SW4) and the relay coil, so that current eill only flow through the coil when SW4 is closed. As shown, it is also sensing the string PR2A, SW5, and that pushbutton What is shown is a parallel circuit.
 

MisterBill2

Joined Jan 23, 2018
18,167
An isolated 5 volt supply is what the TS would need to provide. It can feed from the mains and does not need to provide more current than the relay requires. Probably one of those really cheap cell phone chargers will work.
 
My solution involves J15, J16 and J17.
Place a resistor across J15 and J16 such that I= 24/ R(PR2)+Rx ~ 1.5 to 2mA
R(Pr2) is the coil resistance of PR2
Now put a 1 mA optocoupler with resistor such that R(LED) = (24-2.1)1.5mA; The 2.1 from the datasheet

Now you have an isolated contact to do what you want with.
5V, Pull-up resistor, whatever.

Whether or not this will work depends on the relay. I picked a relay out of the hat and got 2800 Ohms or 8 mA. That might not work.

This 24Vdc relay has the following specs:
https://www.digikey.com/en/products/detail/idec/RH2B-UD-DC24V/8344807

Must Operate Voltage19.2 VDC
Must Release Voltage2.4 VDC
Coil Current37 mA


It stands a chance at working if 2mA would not cause the opto-relay to operate.
 

sghioto

Joined Dec 31, 2017
5,376
Correct.
My solution involves J15, J16 and J17.
Place a resistor across J15 and J16 such that I= 24/ R(PR2)+Rx ~ 1.5 to 2mA
R(Pr2) is the coil resistance of PR2
Now put a 1 mA optocoupler with resistor such that R(LED) = (24-2.1)1.5mA; The 2.1 from the datasheet
I show that in post #25, but only works if the TS has access to J15 or ground.
 
Top