Killed my first propeller today

smbaker

I'm still trying to figure out what happened... Let's say I accidentally hit some pin in the range of P11 to P19 with +12V. Would that destroy only those IO pins, or would it destroy other pins as well? This shouldn't have happened, but it's the only thing I can think of (I'm connecting a 12V device to the prop which has open collector outputs tied to those input pins).

Propeller tool still thinks it is able to program the EEPROM.

Does anyone make a propeller tester board?

Scott

localroger

There's something about the overvoltage circuitry that seems to like to get fried.

I had an oddly different experience. I designed a PropMini into a board as an accessory for a device which uses 5V logic. I used 1K resistor packs to buffer the voltage difference having forgotten the long-ago thread where 2.2K was calculated to be the minimum advisable Most of the boards just worked but about 20% failed, and the failure was general, not pin-specific. Like yours the PropTool would still program them but the other I/O pins wouldn't respond. Also the Zener clamps continued to function. I redesigned the board with 3.3K packs and external zeners on a couple of lines that are bidirectional and didn't work through the higher resistance, and all seems OK.

smbaker

So what is the best way to protect my inputs from overvoltage (without going overboard like optoisolators)? This happened when I hotplugged the device in that I was interfacing to. I'm guessing what happened is that the 12V connected before the GND, and momentarily pulled all of the inputs up to 12V, and that nuked the propeller. Prior to my hamfisted hotunplug/hotplug, the circuit was working fine. Aside from affixing a label 'don't hot plug', what should I do? Would adding my own 3.3V zeners suffice? I have 10 IO pins that I need to protect.

Rayman

Sadly, I've also fried a few Props via overvoltage... What usually dies first is the PLL. If you tried running in RCFAST mode (20 MHz) it might still work.
For protection, a large series resistor to I/O pins is often enough. The Prop has protection diodes on all the pins already.
If you want to be extra careful, a zener diode or unipolar TVS (for fast pulses) might be a good idea so as not to stress the Prop's protection diodes.

T Chap

A schematic would be helpful. If this is for a product, then you should have a circuit that provides robust plug and play protection. Even with labels and warnings, people still ignore that stuff and hot plug cables all the time. A device like some Cmos 4050 variants will allow an input from 3v3 up to 15Volts without damage, and you can get 6 in a 16pin dip. Use a pull down on the inputs in case the input is not connected. One IC can take about the same space than 6 zeners.

LoopyByteloose

I suspect the short story is to avoid hot plugging altogether.. if you can. That will save you a lot of extra thought and construction.

Boards with damaged i/o are not really useless. I have one that I generally use for sloppy impulsive explorations. I save my good ones to commit to a final build.