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Heat problem — Parallax Forums

Heat problem

halfblinddadohalfblinddado Posts: 59
edited 2009-03-14 01:19 in BASIC Stamp
Hello,

I put a small breadboard on a super carrier board to do some experimenting. On the breadboard I have a uM-fpu, a compass module and a gps module all hooked up to the stamp. I connected some long wires from the board to the gps module so I could put it next to a window where it receives a signal.

The problem I have is that the heat sink on the board gets very hot and on a few occasions the board has turned off. Is this due to just overloading the board or are the long wires to the GPS module causing it?

Also' will this damage the stamp?

Thanks,

Mike

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"Everything is working so why do we pay him?"


"Nothing is working so why do we pay him?"

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-13 22:17
    The excess heat could be due to several factors:

    1) Your power supply could be relatively high. Anything greater than about 5V is just turned into heat (power as heat = voltage above 5V x current drawn). The regulator does require at least 5.5 to 6V to regulate properly.

    2) Your breadboard could be drawing too much current. GPS modules tend to be relatively power hungry or you may have a short on your breadboard.

    3) If the regulator (and board) is in sunlight, that will increase the operating temperature which will worsen the problem somewhat.

    The Stamp should be ok unless there's something wrong with the wiring and there's a short circuit somewhere. Even then, it's pretty robust. Stamps tend to be damaged by connecting the power source backwards or by connecting the regulated power input to something over 5V.
  • sylvie369sylvie369 Posts: 1,622
    edited 2009-03-13 22:47
    Can we assume that your circuits are doing what you wanted them to do? That is, you're getting GPS and compass data to the Stamp?

    I'd think that if you are, then a short circuit is quite unlikely. But if the circuit is not working, I'd think a short circuit would be easily the most likely culprit, right?
  • halfblinddadohalfblinddado Posts: 59
    edited 2009-03-14 00:10
    Yes everything is connected and working. It only seems to have the problem when·connect·the the GPS and then it's intermittent.

    The wires I am connecting the GPS with·are about 5' long and I am using the parallax 12v power supply.

    Thanks,



    Mike

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "Everything is working so why do we pay him?"


    "Nothing is working so why do we pay him?"
  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-14 01:19
    GPS units tend to draw a lot of power compared to other devices and you're using a power supply well above the minimum required. For example, Parallax's GPS receiver takes 115mA. With a 12V input to the regulator, thats (12V - 5V) x .115A = about 0.8W. The compass, FPU, and the Stamp itself draw relatively little current. Your best solution is to use a lower supply voltage. I'd suggest no more than 7.5V if possible. If you can't do that, put another regulator in line with the 12V supply. You could use an LM7808 regulator to drop the 12V to 8V which could then power the Super Carrier Board. Look at the datasheet for the LM7808 to see what the recommended input and output capacitors should be. You may need a small heatsink on the LM7808.
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