I’m thinking about using LED-lit switches on a breakout box. The goal would be that when the circuit is closed that an LED would illuminate. Does anyone know what the voltage is across the terminals?
Thanks in advance.
Thanks in advance.
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Thanks @Biglew11 That would explain why no one is using illuminated switches or status LEDs. I suppose I could just pit a DC voltmeter across it and see what the voltage is. If I decide to hack something with status lights on a BoB I’ll make sure to post.Any where from 2.5v to 5v, and not enough current to drive anything just enough to sense weather a switch is open or closed.
it may be doable with a digital type sensing circuit. but it would probably cause interference with the breakout box being able to sense an open or closed switch.Thanks @Biglew11 That would explain why no one is using illuminated switches or status LEDs. I suppose I could just pit a DC voltmeter across it and see what the voltage is. If I decide to hack something with status lights on a BoB I’ll make sure to post.
Thanks @Biglew11 That would explain why no one is using illuminated switches or status LEDs. I suppose I could just pit a DC voltmeter across it and see what the voltage is. If I decide to hack something with status lights on a BoB I’ll make sure to post.
Thanks @theatrus -- my thought was that once I know the open circuit voltage that I could put an appropriately sized LED in series with a switch. Of course I would simply put the LED across the port to see what happens -- and hopefully not let out any of the magic blue smoke.It uses pull-ups and series limiting resistors, which doesn't allow for powering directly from the port. Putting any load on it should drop the voltage pretty quickly - don't just measure open circuit voltage.
Thanks @theatrus -- my thought was that once I know the open circuit voltage that I could put an appropriately sized LED in series with a switch. Of course I would simply put the LED across the port to see what happens -- and hopefully not let out any of the magic blue smoke.
Thanks @NinjaTiLL -- I figured it would be very low current but never really dug into the specifics. So this is very helpful. I'm going to rethink the "cool factor" vs "effort" side of this.This will not work. This is a sensing circuit only. The controller most likely has pull-up resistors on each pin that only allow micro-amps to pass through the resistor to pull the pin high. When you connect a switch to the break out box, the switch connects the pin to ground. The controller senses the low state and acts upon it.
I tinker with microcontrollers all the time. I do not know the specifics of what is inside the Apex. But, most uCs use about a 47kOhm pull-up resistor. If we assume it is 5V (TTL) logic, then the pull-up resistor passes 106uA. That is not enough to power an LED indicator and would mess with the I/O pin state anyways (since most LEDs have a 2V or more forward voltage.) Most newer uCs use 3.3V logic and, if that is used here, the same 47kOhm resistor only passes 70uA. Most LEDs require about 20mA. I've seen LEDs that use single digit mA but those are rare, and dim. I've never seen an LED that pulls less than 1mA.
Good luck, let us know what you find.
There's another angle to consider. You could use a DPST (double pole single throw) switch and a separate power supply to accomplish the same thing. One side of the switch would connect to the Apex BoB and ground. The other side of the switch would connect to a separate (probably 5v) power supply, the led, a current- limiting resistor and ground. Do you need a schematic?Thanks @NinjaTiLL -- I figured it would be very low current but never really dug into the specifics. So this is very helpful. I'm going to rethink the "cool factor" vs "effort" side of this.
this will work very well if op doesn't mind a separate indicator light.There's another angle to consider. You could use a DPST (double pole single throw) switch and a separate power supply to accomplish the same thing. One side of the switch would connect to the Apex BoB and ground. The other side of the switch would connect to a separate (probably 5v) power supply, the led, a current- limiting resistor and ground. Do you need a schematic?
Here is one that uses LED switches, the LEDs only go on when the switches are in the ON position. It does not send power to the BOB. the power is on a separate circuit.
available here
They are the standard 3-prong LED toggles. Yes each switch has a relay.What toggles are you using, that have LEDs on a separate circuit? Those aren’t the standard 3-prong LED toggles? Or are you incorporating individual relays?