Electric Circuit - Power Supply Issue

I'm new to electrical circuits and the Arduino board in general. I'm creating a simple project in which the Arduino board simply controls a 12v desktop case fan via a light sensor. If the amount of light is high, the fan speed is high, if it's low the fan speed is low or off. That's just the general overview of what I'm trying to accomplish, but my issue is not really related to that.

So currently in my circuit, I've got a light sensor, switch, two LED's, a CMOS Motor Driver - RFP30N06 which says its supporting 30A/60V, and either a 9v powersupply or a 12v powersupply.

The arduino board is connected via USB, and the fan is utilizing the external power supply of either 9v or 12v.

The light sensor, switch, and LED's are being powered from the Arduino board. The switch and light sensor are from the 5v's and LED's just from the digital inputs.

The fan and the cmos motor driver are both powered from the power supply, where the Fan is grounded to both the arduino and power supply, and the driver is grounded to only the power supply.

My issue is this; when the circuit is in the off position (the fan is not allowed to spin) my 12v power supply begins to heat up and the wires connected from the power supply to the breadboard start to overheat and melt. However, if the circuit is in the on position (the fan is spinning) then everything is fine and works as intended.

Also note, that this circuit runs fine with a 9v battery. I'm able to turn the fan off and on without and overheating issues, however the fans speed is much lower due to less power. Running on a 9v battery causes another issue achieving different speeds for my fan, as I noticed when I was attempting to control the fan (say I wanted half the speed), I would input some code, and instead of the fan spinning, a whining sound would occur as I guess the code was controlling the amount of volts going to the fan.

So, how would I prevent this 12v power supply from overheating... as I'm guessing the issue is that the power has no where to go and is just being held in the wires.

Is the 12V supply a switchmode supply?

I don't think so,

http://www.thesource.ca/estore/product.aspx?language=en-CA&catalog=Online&category=BatteryAccessories&product=2700387

This is the one that I'm trying.

So, how would I prevent this 12v power supply from overheating... as I'm guessing the issue is that the power has no where to go and is just being held in the wires.

LOL, Whatever the root cause of your problem I can assure you that it's not because of anything being 'held in the wires' because it doesn't have anywhere to go.

Only with a posted schematic drawing of your complete wiring setup can anyone do more then a wild ass guess of what might be wrong.

Lefty

What is the spec of the 12V supply?
What is the rating of the desktop fan?
Is the supply powerful enough to drive the fan?

Bear in mind breadboard connections are good to 200mA to 500mA or so, put too much current
through and you'll ruin it - high current wiring best done with screw connector blocks which are
rated 5A, 10A etc.

BTW the common ground point is ideally at the motor driver since thats where signal levels meet high-current
circuitry.

retrolefty:

So, how would I prevent this 12v power supply from overheating... as I'm guessing the issue is that the power has no where to go and is just being held in the wires.

LOL, Whatever the root cause of your problem I can assure you that it's not because of anything being 'held in the wires' because it doesn't have anywhere to go.

Only with a posted schematic drawing of your complete wiring setup can anyone do more then a wild ass guess of what might be wrong.

Lefty

Lmao, like I said I know nothing of circuits and I'm not even studying Electrical Engineering.

MarkT:
What is the spec of the 12V supply?
What is the rating of the desktop fan?
Is the supply powerful enough to drive the fan?

Bear in mind breadboard connections are good to 200mA to 500mA or so, put too much current
through and you'll ruin it - high current wiring best done with screw connector blocks which are
rated 5A, 10A etc.

BTW the common ground point is ideally at the motor driver since thats where signal levels meet high-current
circuitry.

Spec of 12v supply? I'm not sure... I'm using the one I posted which is 12 volts of power via 8 AA batteries.

Fan rating- it's a 12 volt DC fan, 0.16 A 3 wire red black yellow

Model #-CM A12025-12CB-3BN-F1

Yes the power supply is enough to drive the fan, it's 12 volts.

I'm curious in what usual case would the power supply overheat if a circuit is in the off position vs it's allowed to run?

Is there some sort of code that could stop the current from being drawn? I think when my switch is off, I'm drawing a current, but not doing anything with it.

Or perhaps this is a grounding issue? I noticed in the off position when I powered this off a 9v, the battery got fairly hot, but nothing was melting and the wires were fine.

Is it possible that the wires connected to the PSU are just shit? They do appear to have a smaller diameter than the ones I'm currently using in the rest of my circuit.

like I said I know nothing of circuits

You don't need to know anything about circuits to draw a sketch of how you have connected everything. You explained it, after all, earlier on, so you do know what you have. It's just difficult for others to follow the words, rather than the pictures! Give it a try.... draw each of the items as blocks at least... the fan, sensor etc etc, and join them up with lines to represent the wires. Label all the components and their terminals (like eg Battery + and Battery -).... then we might get a better idea of what you have.

I'm curious in what usual case would the power supply overheat if a circuit is in the off position vs it's allowed to run?

Is there some sort of code that could stop the current from being drawn? I think when my switch is off, I'm drawing a current, but not doing anything with it.

I think it's likely that when it's off your circuit is shorting something so that yes there's a current, but as a short circuit (little or no resistance) rather than a nice load which would explain the melting.

All the more reason to draw a sketch of the circuit so others can have a look...

Yea, I might get around to drawing a circuit for you guys. After this one question though; I just inspected my 12 volt power supply, and noticed the wires are stranded, not solid. Could this be the issue? I know the Arduino is specifically supposed to use solid wires for the circuit, the rest of my wires are solid.

I know the Arduino is specifically supposed to use solid wires for the circuit,

Don't know where you got that from?- it's usually suggested that you don't use stranded wire in breadboards since they often bunch as you push them in, making for bad connections. Also bits break off and block the holes.

Yea, I might get around to drawing a circuit for you guys.

.... we might get around to helping.

It sound like you have some short when your fan is switched off.

My guess is that your 9v battery is a PP3, in which case the reason you're not seeing the same overheating/melting issues with the 9v is nothing to do with the voltage but actually the batteries inability to supply high current.

I also suggest all grounds get commoned as you could also have a path back through other components. Strange things can happen when you forget to reconnect all your grounds together.

Without a drawing of what you actually have then your not going to get any further wit help.

Its a short, that's clear - multimeter time (well actually multimeter time is after putting the circuit
together and before first applying power - always check for power supply shorts with a new circuit).

MarkT:
(well actually multimeter time is after putting the circuit
together and before first applying power - always check for power supply shorts with a new circuit).

Yeah, right.....