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Switch jack

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conrad taggart05/05/2019 17:16:52
99 forum posts
5 photos

The diagrams below are for a switch jack whereby you can fit it to a fly wing for example and bury the receiver and battery in it . When you pull the jack out of the switch it will automatically turn the receiver on and turn it off again when you re-insert it into the switch. Plus when ithe jack is inserted you can connect it to your battery charger and charge the battery , via the servo lead that is attached to the jack.

Could someone please help me read / understand the bottom diagram relating to the wiring of the mini jack plug ? Is the diagram indicating that the centre pin of the jack plug should have the negative wire soldered to it and the outer side / sheath should have the positive wire attached to it ? Thanks taggarc



Edited By conrad taggart on 05/05/2019 17:18:41

Martin Harris05/05/2019 18:42:33
8944 forum posts
221 photos

As far as I can see, the negative connection is to the sleeve and only there for charging through the jack plug. The plug would simply be wired positive to the centre and negative to the sleeve of the cable from the charger.

The plug action breaks a connection between the battery and receiver positive and one side is left connected to the battery - you'd need to confirm which one by testing unless any more info is available. There will need to be a connection to both the receiver and battery negative soldered to the middle pin.

My main concerns would be the current rating - the jack specified is tiny - 0.101" sleeve diameter if my research is correct and there is no current rating specified and the presumed lack of any wiping action in the internal contact. These factors may easily lead to high resistance, overheating and failure if any meaningful loads are carried.

Edited By Martin Harris on 05/05/2019 18:57:56

MaL06/05/2019 11:14:15
140 forum posts
13 photos

Also of concern is the fact that when using the 2.5mm or 3.5mm audio jack plugs as shown as 502-855 is that they can easily short between tip and sleeve as you insert the plug into the socket... not such a good thing when dealing with a power connection. The DC power type of plug and socket as shown as 502-712A and 502-765 cannot short between pin and sleeve when inserting the plug so are a much better choice for this application, however, the contact between the battery +ve and the receiver +ve can be dodgy if subject to vibration and/or dirt as the contact area is both small and just nickel plated. Maybe OK for a glider but I wouldn't use one for a powered model.

Steve J06/05/2019 11:52:05
1617 forum posts
49 photos

The Switchcraft minijack is rated at 2A so should be OK for the application.

As I read the sketch, the tip of the jack is positive.

I have made the circuit that uses the 712A and have them in a couple of gliders. In this case the centre is negative.

Always ring this sort of thing though before connecting to anything.


conrad taggart11/05/2019 17:26:57
99 forum posts
5 photos

Thanks guys - worked a treat - embedded in a flying wing. Maximum charge it ever gets is 0.30 of an amp

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