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Schematic help - contact sense
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anishkgt:
Hello All,

I am trying to sense when two electrodes makes a contact. I've put up a schematic, partially completed. How can i trigger the T1 when the electrodes the short.

Would appreciate if any one could help or suggest me a better option.
JVR:
How about telling us what the contacts are, and where they are used. Since that schematic looks like overkill, unless some context and constraints are elaborated upon.
anishkgt:
Oh sorry, it’s spot welder. When triggered the electrodes have 2vac at the electrodes and several amps to spot weld nickel strips to 18650 cells.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

Sent from my iPhone using Tapatalk
JVR:
I'd suggest a current sense method, as I assume open circuit the voltage will be higher.
anishkgt:
2vac is actually the open circuit voltage.

Yes sounds like a better idea to sense the current.  So how many ohms resistor should I go with ? Through hole or smd ?

The resistor would go in parallel with one of the cable and two wires form both sides of the resistor the add of the muc, correct ? Would it be a good idea to sense the current during the weld also ?


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

Sent from my iPhone using Tapatalk
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