Strange problem with jack plugs

A customer let me have 2 stapling machines that the operators had damaged all the wiring that triggers the action

it was a 3.5mm jack socket with a switch in it to short the live to earth when the plug isn’t in it.

the 2 wires from the 3.5mm plug go to a foot switch with a nc v3 micro switch

when the plug isn’t in the machine theres a switch that operated by the action of putting paper in whilst in flat mode. The foot switch is used when saddle stitching.

so i thought I’d upgrade the sockets and plugs to 1/4 versions..however when i did this the machine wont work.

if i have the 2 wires coming out of the machine and hold them in my hands with me holding the bare conductors and disconnect them the machine wont trigger if i hold by the insulation it triggers when broken from its nc state.

so thats resistance from my skin?

but why wont these sockets and plugs work?

I know thats a stereo socket and a mono wire….the socket isn’t damp.

the 3.5mm in the picture is what was fitted.

any ideas?

Just another point if i have the machine switched on ready to go with no plug in the socket and remove one wire from the socket the machine triggers..place the wire back on and off again and it triggers …so its just like the socket is shorted..but my meters show no short.

At first glance, does the ¼" socket have an NC switch twixt tip and sleeve?

Bill

Bill

it has 3 nc switches one for each pole

Have you wired the switches to short tip to sleeve when the plug is removed?

This is usually intrinsic to the design of 3.5mm sockets, but needs to be wired in for the 1/4" socket in your picture - There needs to be a wire between the sleeve contact and the *switched* contact on the tip for it to function like the 3.5mm one.

I recall having trouble in the past using mono plugs in stereo sockets. The tip of the mono plugs was more generous in length than those on the stereo plugs and the centre contact on the stereo socket landed across the insulator ring and shorted the plug.

Try placing an insulated wedge into the centre switch contacts to lift it clear of the plug and use the outer pair of contacts.

Keith

At the moment theres only 2 wires one to the sleeve and one to the tip and if i put a plug in good continuity to the wires and no measurable short.

the electronics in the stitcher head must be very sensitive to the resistance between poles on this brand of sockets

Chief suspect is that stereo socket. I agree with Keith - mono plugs often don't fit properly into stereo sockets. The mismatch is best avoided because it's uncertain what makes contact with what and when. Using a stereo socket also introduces the wiring uncertainty mentioned by Andy.

The stapler's electronics are likely to be sensitive which would explain some of the odd behaviour. Almost certainly the stapler contains a high-gain amplifier arranged to debounce a correctly wired switch. The debounce circuit is probably built from high-impedance (voltage driven) semi-conductors that could respond to mains hum or radio frequency interference if the circuit isn't terminated properly. Testing anything electronic by manually manipulating dangling wires is likely to mislead. Electronics are orders of magnitude faster and far more sensitive than power electrics so the sort of temporary lash-up that's good enough for deaf as a post electricity, is likely to introduce a multitude of side-effects that electronics will react to.

Fitting a normally closed mono socket might well be enough to restore order.

Dave

You have not answered Andy_g's question. Have you put a link wire between the two switched terminals on the 1/4" socket? If you don't do this then when the plug is out of the socket the two wires going to the socket do not make a closed circuit.

Martin C

Before using the switched function on the sockets i was trying to get it to work with just 2 wires one to tip and one to sleeve..nothing I could do made any difference.

bought another brand of sockets and problem went away..so i now have a bag of 10 3 pole 1/4 sockets spare..

Edited By Ian Parkin on 01/08/2022 18:14:55