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Author Topic: Switches  (Read 763 times)

Peter34

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Switches
« on: May 22, 2019, 07:42:56 PM »

Hi.


Is there a way to use a spst switch to turn on 2 circuits. I know you would normally use a double pole switch but can't find one thats suitable, as I need a 12v 16mm round waterproof one.


The switch would be to turn the escs on once the batteries are connected. I have 2 escs and a battery for each. I dont know if it was possible to just wire the 2 esc on/off switches together.
 
Thanks


Peter.
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DaveM

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Re: Switches
« Reply #1 on: May 22, 2019, 08:07:16 PM »

Peter

If I read your post correctly then you want to switch two totally independent circuits with the same single pole changeover switch.

Not possible, I'm afraid.

This would do the job but it's not waterproof https://www.technobotsonline.com/12v-20a-dpdt-toggle-switch.html

DaveM
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Peter34

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Re: Switches
« Reply #2 on: May 23, 2019, 06:21:45 AM »

Thanks dave thought that might be the case.
What about if I only used one battery for both escs?
Or used 2 batteries but wired in parallel or would that not make any difference.
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DaveM

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Re: Switches
« Reply #3 on: May 23, 2019, 08:22:03 AM »

Either of those options would be OK.
DM
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warspite

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clockworks

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Re: Switches
« Reply #5 on: May 23, 2019, 10:29:47 AM »

Is this switch to go between the main batteries and the ESCs?
I wouldn't think that was a good idea, unless the motors are really tiny low current ones, or you use the switch to activate a big relay, and wire the relay contacts between the battery and ESC.



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Peter34

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Re: Switches
« Reply #6 on: May 23, 2019, 10:53:30 AM »

The 2 escs I have, have an on off switch on them.
I want to be able to turn both escs on and off from the same switch.
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DaveM

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Re: Switches
« Reply #7 on: May 23, 2019, 10:59:14 AM »

I think we've covered this a few times before - or certainly Malcolm Frary has. Switches are rated at the current they can carry at the moment of turning them on i.e. instantaneously, whereas once the contacts are closed then they are capable of conducting more than that value. Model boats are slightly different from mains appliances in that usually no load is turned on immediately by the power switch (except maybe a few indicator LEDs). You have to operate the throttle for the motors to run and draw any appreciable current from the battery.
That said, I wouldn't be happy about using a switch rated at just 6A for connecting up the battery to the speed controller(s) in a 12v system whereas the 20A one from Technobots would be fine - that's why they sell them for robot models with big 24v DC motors.
The small switches on the ESCs are most probably for controlling the onward 5v supply from the BEC to the receiver; they don't switch the connection to the main battery.
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RST

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Re: Switches
« Reply #8 on: May 23, 2019, 11:01:57 AM »

Do you have one esc with the bec disabled? Is it possible just to leave that one switched on (or cut switch off and join the wires), and use the switch on the other esc? Can replace it with whatever switch and some extended wires you like then.
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malcolmfrary

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Re: Switches
« Reply #9 on: May 23, 2019, 11:06:29 AM »

The 2 escs I have, have an on off switch on them.
I want to be able to turn both escs on and off from the same switch.
I was going to say what DaveM just said - the esc switches just decide whether or not the ESC control circuit is on or not.  Not knowing exactly what is going on inside the ESC, there is no safe way of just having one simple switch do the job, BUT it is possible to have two electrically separate switches in the same case operate together mechanically.  This is called a double pole switch.  Similar size to the one on the ESC as supplied, but twice as wide.  Can be done, but generally pointless - just mount the two switches side by side where you can see them.
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clockworks

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Re: Switches
« Reply #10 on: May 23, 2019, 11:12:53 AM »

Do you have one esc with the bec disabled? Is it possible just to leave that one switched on (or cut switch off and join the wires), and use the switch on the other esc? Can replace it with whatever switch and some extended wires you like then.


That's what I would do if it really wasn't possible to use a double pole switch, or 2 separate switches.


With the receiver disabled by turning off the ESC that has it's BEC connected, the other ESC won't be doing anything much. Will still draw a little power from the battery though, but fine for a few hours.
Best to actually disconnect the batteries until you get to the lake, then use the ESC switch to "arm" the boat when it's actually being used. Disconnect the batteries again when you have finished for the day.


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Peter34

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Re: Switches
« Reply #11 on: May 23, 2019, 12:12:36 PM »


That's what I would do if it really wasn't possible to use a double pole switch, or 2 separate switches.


With the receiver disabled by turning off the ESC that has it's BEC connected, the other ESC won't be doing anything much. Will still draw a little power from the battery though, but fine for a few hours.
Best to actually disconnect the batteries until you get to the lake, then use the ESC switch to "arm" the boat when it's actually being used. Disconnect the batteries again when you have finished for the day.


That's not a bad idea. Could I still have the 2 separate battery circuits or would I be better wiring the 2 batteries in parallel.
I was trying to upload a circuit diagram of what I wanted but I can't for some reason.
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clockworks

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Re: Switches
« Reply #12 on: May 23, 2019, 12:21:29 PM »

Would work either way, but it would be easier to have the batteries wired in parallel - just one pair of connectors to plug in when you get to the lake, and the batteries would be balanced.


I guess it depends on how the components are laid out in the boat, and how the wiring would be routed
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malcolmfrary

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Re: Switches
« Reply #13 on: May 24, 2019, 10:04:05 AM »


That's what I would do if it really wasn't possible to use a double pole switch, or 2 separate switches.


With the receiver disabled by turning off the ESC that has it's BEC connected, the other ESC won't be doing anything much. Will still draw a little power from the battery though, but fine for a few hours.
Best to actually disconnect the batteries until you get to the lake, then use the ESC switch to "arm" the boat when it's actually being used. Disconnect the batteries again when you have finished for the day.
Over-thinking solutions to problems that don't exist usually results in actual problems that are hard to fix. 
Just mount the two small switches that the ESCs came with alongside each other so that the same finger can operate both at the same time, preferably mounted where they can be seen.  When they switch off, the circuit really is OFF as opposed to letting one ESC permanently draw its quiescent current.  If the need is felt to have an extra fault liability between battery and ESCs, fitting a fuse is the nearest to useful.
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clockworks

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Re: Switches
« Reply #14 on: May 24, 2019, 10:20:15 AM »

Over-thinking solutions to problems that don't exist usually results in actual problems that are hard to fix. 
Just mount the two small switches that the ESCs came with alongside each other so that the same finger can operate both at the same time, preferably mounted where they can be seen.  When they switch off, the circuit really is OFF as opposed to letting one ESC permanently draw its quiescent current.  If the need is felt to have an extra fault liability between battery and ESCs, fitting a fuse is the nearest to useful.


I'd agree with you about keeping it as simple as possible, but the OP said he needed to use a round, waterproof, switch of a specific size, and couldn't find a double pole version.


Raises another question in my mind though - does switching off an ESC with the switch fitted by the manufacturer actually turn it off completely (no current drain at all)?
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malcolmfrary

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Re: Switches
« Reply #15 on: May 24, 2019, 10:36:47 AM »


Raises another question in my mind though - does switching off an ESC with the switch fitted by the manufacturer actually turn it off completely (no current drain at all)?
With modern components, as near as makes no difference.  The component leakage of the output transistors (the only parts presented to the battery supply) is probably less than the self discharge of the battery, so there would be no way of telling the difference.  The control circuit, even when seemingly doing nothing, is generally quite busy doing nothing as far as drawing power is concerned.
As to waterproof switching, on the Micro Magic, Graupner use a pushrod via a bellows.  Two of them would also work well.  Probably a lot easier than trying to arrange a single linkage to work two switches together reliably.
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Peter34

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Re: Switches
« Reply #16 on: May 30, 2019, 09:19:14 PM »

I've cut the switch of the escs. If I put my multimeter across the wires. They have full battery voltage running through them, so 12v.


I think I read above that if the batteries were wired in parallel then I could connect both sets of switch wires together and use an on/off switch to turn them on and off after connecting the main batteries.


If the above isn't true. I have a spst switch with an led. It has the following connections, +, -, no, nc, common. Can I use this to replace the simple on/off switch that was on the esc, if so how.



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clockworks

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Re: Switches
« Reply #17 on: May 31, 2019, 10:12:30 AM »

That's an SPDT switch, but you can use it as SPST. Just connect the 2 wires to the common and NO terminals.
The + and - are power to the LED.


With a DT switch (3 terminals per pole), the common terminal is connected to the NC terminal when the switch is in the "off" position, and the common terminal is connected to the NO terminal when the switch is "on".


It doesn't really matter whether you use NO or NC - that will just alter which way the toggle or rocker is facing when you switch the circuit on.



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malcolmfrary

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Re: Switches
« Reply #18 on: May 31, 2019, 10:15:04 AM »

There is no safe way to easily determine just what the ESC switch wires are connected to - if the question is asked on a forum like this, there is the danger of the responder taking the wrong part of a question that contains abiguities, however unintentional, and the asker also getting hold of the wrong end of the stick from what could easily be the right answer to the wrong question.
 
The switch descibed is usually a change-over switch (with its 3 terminals) plus, in the same box, an LED plus a resistor to let it work on the stated voltage.
With the switch "off", nc and common are connected.  With the switch "on", no and common connect.  If the contacts are strong enough, the switch can be inserted into the power leads of both ESCs. 
I can think of no circumstances where I would connect the internal circuits of two boxes without knowing what the internal circuits were.
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