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Ping Current Draw — Parallax Forums

Ping Current Draw

BajaBobbyBajaBobby Posts: 3
edited 2009-11-04 19:04 in Accessories
Does the Ping have overheat/over current protection?

When powering a Ping sensor is it necessary to limit the current?

I have a 8.5V battery connected to a LM7805. That is powering an Arduino a high torque servo and a Parallax Ping.

The 5V regulator got pretty hot as well as the Ping sensor. My estimates are that the whole circuit should have only pulled about 500mA. The LM7805 is rated for 1A.

I'm not sure what was shutting down or got fried. The Ping smelled like I let out the "factory smoke", but it still powers up and blinks. My original test set up had it and a tiny servo powered from the Arduino 5V out. I haven't tried that set up again yet to see if the ping still works.

Anyone have schematics for the Ping?

Comments

  • BajaBobbyBajaBobby Posts: 3
    edited 2009-11-04 05:08
    The good news is the Ping still works, shew thought I trashed a $30 sensor!
  • Mike GreenMike Green Posts: 23,101
    edited 2009-11-04 05:33
    The Ping doesn't have overheat/over current protection because it shouldn't need it

    It is not necessary to limit the current to a Ping sensor

    A high torque servo could draw as much as 1A when mechanically heavily loaded. A Ping should draw no more than 35mA. The current draw of an Arduino board depends heavily on what's attached to it, but it should be under 100mA.

    I don't believe there are schematics available for the Ping. It's designed by a 3rd party.
  • tronsnavytronsnavy Posts: 70
    edited 2009-11-04 09:30
    BajaBobby,
    Yea, I bet your regulator got hot.· The smoke you smelled was probably from the regulator.·· I Had the same thing happen to me about a month ago.· Was running my bot with a 9 volt rechargeable battery.· Normally, driving a 5 volt regulator with 9 volts would not be a problem, unless you draw "above" average current (like 500mA).· If you are drawing that much current, you should probably look into a 7.2-6.0 volt battery (power source)·to drive your 7805.· I bought a 7.2 volt rechargeable battery just a few weeks ago.· My 5 volt regulator is much cooler.· As mike said, Ping will only draw about 35mA, thus it was probably not the problem.· Good luck.
    Bob
  • BajaBobbyBajaBobby Posts: 3
    edited 2009-11-04 18:39
    Thanks for the input.

    I'm pretty sure the Ping was getting hot. I have it temporarily mounted away from the other components. It was hot to the touch and smelled like it fried. Also the circuit shut down when the sensor was idle. So the servo shouldn't have been drawing a lot. Maybe a zener on the +5V of the Ping would help? I do agree the regulator was probably taxed too heavily though. I appreciate everyone's input, thanks.

    I'll draw up a block diagram and post it. Maybe I just have something hooked up wrong.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-11-04 19:04
    A Zener on the +5V of the Ping won't help at all. If there was a problem with the +5V supply, that needs to be fixed at the source. The Ping can be damaged if you try to operate it on more than 5V. It's possible that an electrolytic filter capacitor on the Ping failed due to excess voltage and it eventually burnt up enough so it no longer affects the rest of the Ping and no longer looks like a short circuit. See if one of the little yellow "blocks" on the backside of the Ping looks burnt up. If so, call Tech Support.
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