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switch harness


Tony j
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Hi all

I was wondering if many people use these switches that have the inbuilt charge socket and if you find them useful . I was thinking of fitting one because i do like to test my battery before a flight (that just me ).

I did fit one of those sockets on its own but could not get on with it kept pushing the plug back out must have done something wrong when i set it up anyway that's long since gone with the airframe

kind regards

Tony J

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I have used them in the past but have since replaced them all with switches with charging leads not sockets. Although buying branded makes I found the volt drop across the switch and through the charge socket was excessive (just over 1v in one case).

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No. The ones I've seen have been a bit naff. Maybe you've found a better one.

Personally, I buy switches from RS and do the soldering myself.

**LINK**

I check the battery manually when I arrive before assembling a model. Telemetry also provides an indicator of RX battery health.

I don't understand your second paragraph I'm afraid.

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Hi Nigel

Second paragraph

I bought an adaptor that allowed you to fit the socket from a three wire switch into it so it effectively became a charge socket on the air frame but as i said never got on with it .

Cheers

Tony J

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I've just checked my usual switches (both with built-in charging sockets) using a recently fully-charged 4.8v pack and a 0.3A load checker:

Direct to batt: 5.43v -> 5.27v = 0.16v drop

Etronix switch: 5.42v -> 5.26v = 0.16v drop

JR heavy-duty: 5.42v -> 5.16v = 0.26v drop

I didn't check any of the cheap basic switches because I've thrown them all away.

I presume the voltage drop would be greater in the more resistive switch types relative to direct etc the greater the load applied.

PS: the Etronix switch is the toggle-type within a machined aluminium housing.

Edited By Jonathan M on 17/07/2020 12:23:02

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The fundamental issue with switches for the airborne part of the radio is that they tend to get mounted to the airframe to make them accessible. Because of this, they are subject to more vibration than the rest of the equipment. The receiver is likely to be wrapped in foam, or stuck to a foam or velcro pad. Servos, certainly in engine powered models, are usually supported on the manufacturer's rubber grommets. That leaves the switch, containing sliding metal contacts and reliant on the sprnginess of the metal to keep them in contact, mountedthe side of the model, where it sees the full force of the vibration from the engine, regular dousings in fuel or exhaust residue and airborne dust thown up by the prop wash. Add frequent visits from oily fingers and is it any surprise that they fail?

Some switches have a transverse hole through the projecting part of the slider, if the switch is mounted in foam inside the model, with a thread passing through the slider hole, it can be switched on from outside the model. Adding a pillar for the thread to pass round and the off thread can also be on the same side of the model, away from the exhaust.

As it is single point of failure, there is a lot to be said for having two switches in parallel, or on larger models, two batteries as well.

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Jonathan, I'm intrigued how you measured a volt drop directly connected to the battery? Where were the volts being dropped? How did you measure the "starting" voltage other than by connecting directly to the battery?

Edited By jrman on 17/07/2020 13:18:38

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The voltage drop is that across the switch i.e effectively a low value equivalent series resistor introduced into the supply between the battery and receiver.

It's worth taking apart one of these mechanical switches (even the genuine Futaba/JR etc types) to see just what minimal contact your expensive model is relying on - something else to worry about wink

 

Edited By Cuban8 on 17/07/2020 13:23:26

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Excellent observation (again) Robin. A chum of mine only ever fits two-pole switches to his models for very similar reasons.

jrman - just use a voltage-checker with a digital readout, plug it straight into the battery first and press the 'test' (i.e. apply load) button, then connect the battery to the switch-lead as normal and your checker into the other end (i.e. the end that normally plugs into the receiver.

I have two checkers: the smaller one is selectable for different battery types (NiMh/NiCd, LiPo) and their different standard voltages, then applies a load of 0.3A, and its digital readout gives you absolute figures for each of no-load and 0.3A-load.

The other checker is only for NiMh/NiCd (selectable between 4.8 and 6.0v), applies a load of 0.5A but only has a row of five LEDs to indicate battery charge and drop under load.

I therefore prefer to use the smaller, more explicit one despite its lower 0.3A load.

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