IR Camera burning out power packs - what could cause?

[JeffCharger]

I have an infrared camera where the power pack has burned out 3 times in 4 months. It's continually powered and I've spliced the powerpack into a CAT5 cable.

The camera requires 12v, 500 mA; and the power packs that I've used have all been 12v and over 500mA (think they've been up to 1A). They have all worked fine, but seem to die after a number of weeks+ of continuous operation.

Two of the powerpacks have been salvaged from RIM charging devices. I can't recall where I sourced the other one from.

Any ideas why this would be happening?

 

[Photon]

Could you take another look at the RIM chargers? The charger I have for a RIM BlackBerry says 5VDC @ 0.75A. Maybe you have a different RIM unit?

 

[JeffCharger]

Could you take another look at the RIM chargers? The charger I have for a RIM BlackBerry says 5VDC @ 0.75A. Maybe you have a different RIM unit?

Photon, I've checked another one (I have a box of them) - they're 12V 500mA. They are for the older/original BB units.

 

[Brightan]

Do you have any way of checking the current? At very least, checking the voltage with and without the load attached might give an idea of whether the power supply can handle it.
It seems to me there are the following possibilities
- the current requirement is higher than what is marked
- the current is going higher at some point do to a short in the wiring or water in the unit or something like that
- your power supply might be rated 500mA but isn't really meant for continuous 500mA (do they run hot?)

 

[mustangcoupe]

When wiring up this next one I'd put in inline fast acting fuse slightly larger then 500 mA. this way if it spikes and draws more current the fuse will blow and give you the indication of over current.

 

[ASIHome]

I have an infrared camera where the power pack has burned out 3 times in 4 months. It's continually powered and I've spliced the powerpack into a CAT5 cable.

The camera requires 12v, 500 mA; and the power packs that I've used have all been 12v and over 500mA (think they've been up to 1A). They have all worked fine, but seem to die after a number of weeks+ of continuous operation.

Two of the powerpacks have been salvaged from RIM charging devices. I can't recall where I sourced the other one from.

Any ideas why this would be happening?

Whose camera? I have heard this before on an IR camera where the manufacturer originally listed the specs as 12V 500mA when in reality the specs were 12V 3A.

 

[amirm]

Wild guess here. Beyond the camera spec being wrong on power consumption, the issue could be the long cable having too much inductance load for the way the supply is designed. For example, the RIM power supply never sees such a long wire in its intended use. Being a switching power supply, it will be more sensitive to such issues.

Try finding an old fashion power brick with a transformer and see if it lasts longer.

The other thing is whether there is a loose connection on the camera causing power spikes as it connects and disconnects.

 

[JeffCharger]

....the RIM power supply never sees such a long wire in its intended use. Being a switching power supply, it will be more sensitive to such issues.

Try finding an old fashion power brick with a transformer and see if it lasts longer.

The other thing is whether there is a loose connection on the camera causing power spikes as it connects and disconnects.

It's got a run on the CAT5 for about 40 feet, could this be the issue? I have others that run 100+ feet.

Do you have any way of checking the current? At very least, checking the voltage with and without the load attached might give an idea of whether the power supply can handle it.
It seems to me there are the following possibilities
- the current requirement is higher than what is marked
- the current is going higher at some point do to a short in the wiring or water in the unit or something like that
- your power supply might be rated 500mA but isn't really meant for continuous 500mA (do they run hot?)

I will check the voltage when it's reconnected. I don't have a way of checking that amperage though... just a voltmeter. Although, looking at my meter - it does have a dial setting marked "1/100/250 mA"? I've never used it - don't know what it's for? Any idea?

Regarding HOT, the first powerpack I had (and subsequently stopped working) was really hot, in fact it took an hour or so to cool down after disconnected. What would this indicate?

 

[Brightan]

- 40 feet of cat-5 won't be a problem. Even if the device is drawing a fairly large current and you are getting voltage drop on your cable it just means it would leave less voltage for the device.

Your Voltmeter can measure current but only up to 250mA so that won't help you. (does it have a separate 10 Amp setting?, some do)
If you are interested you can still measure the current with your voltmeter by putting a very small value resistor in line with the power lead and then measure the voltage across the resistor. For example, if you put a 1 ohm resistor in line and you measured 2 volts across it it would mean it is drawing 2 amps (Voltage across resistor divided by the resistance)
The lower the resistance the better so that it doesn't affect the overall circuit as much and creates less heat in the resistor. Also note that in the above example the resistor is going to be dissipating 4 watts of heat! So either make sure it is a big resister or you just connect it for a few seconds. Anyway, you may or may want to go to this extra effort depending on how curious you are.
The powerpack should run warm but not hot to the touch. It is either working beyond its capability or it's defective. Heat is the death of all electronics