How to wire a flashlight?

[TimTheGreat]

Our team wants to wire a normal 5v led flashlight to the robot and be able to turn it on and off. What is the best way to wire it?

[Matt C]

It would be part of a CUSTOM CIRCUIT and need to be controlled in accordance with R53, and not violate R41, R55, R59, or any other rules I may have missed regulating CUSTOM CIRCUITs.

[TimTheGreat]

Originally Posted by Matt C

It would be part of a CUSTOM CIRCUIT and need to be controlled in accordance with R53, and not violate R41, R55, R59, or any other rules I may have missed regulating CUSTOM CIRCUITs.

mhmm....and what exactly would this custom circuit be?

[MrForbes]

We put a spotlight on our robot...a cheap $14 unit from Walmart. We only used the LED and reflector from the spotlight. The custom circuit consists of a LM7805 voltage regulator and 3.6 Ohm 5 Watt series resistor, and it also uses a Spike relay. The relay is controlled by a relay output on the roborio.

http://www.simple-electronics.com/20...regulator.html

in case you don't know how to figure the resistance and wire up this type of custom circuit.

[JR0405]

You would need to use a relay wired to the Roborio and power the flashlight through the relay from the voltage regulator module

[SuperBK]

Also, you could use a resistor sized with 12 volts in mind and avoid the 7805. And like Mr. Forges says, control the 12V with a spike. Depending on how much the led draws, some teams have run them off a port of the pneumatics control module, though personally, I would prefer to use a spike.

[rich2202]

Depending upon the amps, you might be able to power it off the 5v supply of the VRM. You would still have to have that power go through a relay.

[Ari423]

Originally Posted by rich2202

Depending upon the amps, you might be able to power it off the 5v supply of the VRM. You would still have to have that power go through a relay.

I thought that custom circuits powered through a Spike would need to be powered off the 12V PDP output. I guess you could consider the Spike as part of the custom circuit and power it all off the VRM, but I don't know how much the inspectors or Spike will appreciate that.

[rich2202]

Originally Posted by Ari423

I thought that custom circuits powered through a Spike would need to be powered off the 12V PDP output.

There is no requirement that a Custom Circuit be powered off a 12V PDP output. The rules say a Custom Circuit can have up to a 40A breaker. I could not find a rule that says a Custom Circuit cannot be connected to the VRM.

However, looking at the Spike, it needs at least 9.5 volts, so it will not work switching 5 volts.

So, the custom circuit would need its own custom switch.

[Peyton Yeung]

Both when I was a senior in high school and this year (junior in college) we used a spike relay and voltage converter to turn on the flashlight through the PDP.

We used this flashlight. It's a 3V flashlight so we used this voltage converter. The flashlight was cut in half through the body and wires were added to the + terminal and the body (- side). This was connected to the voltage converter which was connected to the spike relay.

[TimTheGreat]

Originally Posted by Peyton Yeung

Both when I was a senior in high school and this year (junior in college) we used a spike relay and voltage converter to turn on the flashlight through the PDP.

We used this flashlight. It's a 3V flashlight so we used this voltage converter. The flashlight was cut in half through the body and wires were added to the + terminal and the body (- side). This was connected to the voltage converter which was connected to the spike relay.

...Are the voltage converters from the years of the cRIO allowed? We still have ours.

[rich2202]

Originally Posted by TimTheGreat

...Are the voltage converters from the years of the cRIO allowed? We still have ours.

Yes. You could wire a Spark to the PDP, and the output of the Spark goes to the Voltage Converter. That would allow you to turn on/off the voltage converter.

[TimTheGreat]

Originally Posted by rich2202

Yes. You could wire a Spark to the PDP, and the output of the Spark goes to the Voltage Converter.

So we tried connecting the light straight to a talon and limiting the output to 4.5 volts, but it burned out the light. Will that happen with this?

[Peyton Yeung]

Originally Posted by TimTheGreat

So we tried connecting the light straight to a talon and limiting the output to 4.5 volts, but it burned out the light. Will that happen with this?

You should look into how much current is going through the talon at 4.5 volts.

[Alan Anderson]

Originally Posted by TimTheGreat

So we tried connecting the light straight to a talon and limiting the output to 4.5 volts, but it burned out the light.

The output of a Talon is actually either 0 volts or battery voltage. It's pulsed fast enough to yield a variable average voltage, but apparently it's not fast enough to keep the LED from being fried due to too much current.

If the flashlight is happy at 5 volts, then using one of the old 12-to-5-volt converters on the output of a Talon could work. But I'd suggest using a relay (e.g. a Spike) instead of a speed controller, so you never have the chance of making the converter itself unhappy with a PWM'd or reverse polarity input.