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Regulators... Where can I get them? — Parallax Forums

Regulators... Where can I get them?

PhilldapillPhilldapill Posts: 1,283
edited 2007-12-17 22:31 in Propeller 1
Hey, I've been experimenting with the propeller for a couple of weeks now and have even interfaced an LCD module with it. Besides the BS2SX, this is my first real microcontroller experiment. I briefly used the BS2SX a month or so ago and quickly outgrew it's capabilities. I recently got the prop education board and it's great - until you blow the regulator.

Just a couple of minutes ago, I was using·the prop and a pwm signal and a large 12v dc lead-acid battery. Apparently, this is a deadly combo when your messing around with wires will everything is connected. Needless to say, I think I touched the positive lead from the battery to one of the leads on the 5v regulator. I tried firing the prop up, but nothing happens. I'm pretty sure I toasted the 5v. Regulator, and probably the 3.3v regulator since I just replaced the 5v. The only problem is, I don't have any 3.3v regs. on hand.

Anyone know where you can get these for cheap? I looked on ebay, but they're all surface mount. I don't want to pay $8 shipping through mouser or something for such a small part.

Thanks!

Comments

  • parts-man73parts-man73 Posts: 830
    edited 2007-12-16 20:57
    Drop me a Private message with your address and I'll send you some.

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    Brian

    uController.com - home of SpinStudio

    PropNIC - Add ethernet ability to your Propeller!

    SD card Adapter
  • PhilldapillPhilldapill Posts: 1,283
    edited 2007-12-16 21:00
    Oh, btw, for the time being, I'm thinking about maybe dropping in 3 1n4007 diodes to drop the voltage down to ~3.3v for the supply. I think this would have a total voltage drop of about 1.8V. I'd use these because I have 2 full reels... Any thoughts?
  • PhilldapillPhilldapill Posts: 1,283
    edited 2007-12-16 22:00
    Well, it's official. I've toasted my first propeller! I'm so proud of myself... However, I'm not sure if I've toasted the eeprom and the two ADC's that were also connected. When I plug in my MC7805CT regulator, and the 3 diodes in series(for the right voltage drop down to about 3.45V), everything is fine until I connect my 3.45V source to the board, then it seems to short out and all the prop outputs go immediately high. I'm not sure if I screwed up the eeprom and ADC's like I mentioned above. I'm ordering new ones just in case. Any thoughts?
  • Mike GreenMike Green Posts: 23,101
    edited 2007-12-16 22:23
    3 diodes in series is not a good choice for a regulator. If you have some 3V flashlight bulbs that you can wire in parallel to make a load of maybe 100 mA, you could "swamp" the current demands of the Propeller and stabilize the voltage output of the diode string. Do measure the actual voltage across the Propeller. It needs to be kept below 3.6V to avoid damaging the Propeller.
  • PhilldapillPhilldapill Posts: 1,283
    edited 2007-12-16 23:22
    I put the diodes in series with a 330ohm resistor and another 20k resistor in series, but to ground so that it keeps the voltage at 3.45V. The 330ohm resistor goes from the diodes to the 3.3V supply(propeller). This was just supposed to be a temp. setup, which it was - about 2 minutes. I've found that the prop is def. dead. I've ordered all new parts, plus the protoboard with prop,crystal, and eeprom already on it.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2007-12-17 02:02
    Strange that you had 330R in series with the diodes as that would brownout the prop everytime it tried to draw current. Even at 10ma the voltage drop is 3.3V already! You don't need a resistor at all and you will find that the voltage drop of the diodes will increase slightly with increased current. Three diodes could end up with 2.4V drop which is way too much and the minimum would be 1.8V which is just enough. Scrap that idea although I have used red LEDs with a voltage drop of around 1.7V under load to give me a quick 3.3ish supply. I doubt that your prop is dead. Try with just two diodes and no resistors and it should work although I would not normally do this as the unloaded voltage is getting rather close to the absolute max that the prop is "guaranteed" for.

    *Peter*
  • PhilldapillPhilldapill Posts: 1,283
    edited 2007-12-17 05:14
    Yeah.. It's dead, I assure you. But if you want, I can send it to you totally for free if you want to check it out. Any takers?
  • deSilvadeSilva Posts: 2,967
    edited 2007-12-17 22:31
    There a many TO-220 types available for around $1:
    LF 33 (1A)

    LM 1084 (5A)
    LM 1085 (3A)
    LM 1086 (1,5A)

    LM 3940 (1,5A)
    LM 2937 (0,5A)

    Note that they have different pin-outs, either IN/GND/OUT (as expected) or GND/OUT/IN
    Also note the current rating generally means "with heatsink" smile.gif
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