Author Topic: Can RFM69 survive 5V temporary?  (Read 2540 times)

Lensdigital

  • Full Member
  • ***
  • Posts: 151
    • Xronos Clock
Can RFM69 survive 5V temporary?
« on: January 08, 2015, 10:29:36 AM »
Does anyone know if RFM69 will be ok if I send 5V to VCC for a minute or two?  I don't expect it to transmit or work during that time, but in the board that doesn't have voltage regulator, ISP sometimes provides 5V during bootloader upload...
Check out my hand made open source Xronos Alarm Clock!
http://www.xronosclock.com

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6007
  • Country: us
    • LowPowerLab
Re: Can RFM69 survive 5V temporary?
« Reply #1 on: January 08, 2015, 11:45:29 AM »
No it wont

dewoodruff

  • Newbie
  • *
  • Posts: 17
Re: Can RFM69 survive 5V temporary?
« Reply #2 on: January 09, 2015, 01:23:00 PM »
Me being stupid and relatively new to electronics, I originally had an RFM69HW hooked up to a 5v arduino pro mini and couldn't get it working for the life of me. I had it powered probably dozens of times over several hours before I finally realized the voltage difference. I moved it to a 3.3v pro mini and after that it worked.

So I didn't fry it, however, YMMV and it's probably a better idea not to try it if you can avoid it :)

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6007
  • Country: us
    • LowPowerLab
Re: Can RFM69 survive 5V temporary?
« Reply #3 on: January 09, 2015, 01:41:31 PM »
If the DS says abs max is 3.6v on any pin then why are we even discussing 5V?

Lensdigital

  • Full Member
  • ***
  • Posts: 151
    • Xronos Clock
Re: Can RFM69 survive 5V temporary?
« Reply #4 on: January 09, 2015, 01:45:50 PM »
Thanks guys! :) I won't try it then!
I was asking because on the board I'm prototyping, I wanted to program ATMega chip via ISP header before I added voltage regulator. My ISP programmer supplies 5V...  No biggie, I'll just need to supply voltage separate (make and adapter cable)....
BTW speaking of frying things, voltage reversal is of course something else that very bad for ICs, however I keep doing it over and over again (accidentally) and I learned few things on the way. AVRs seem to handle voltage reversals without any ill effects (for a short time) in my experience.  So do some other ICs, like TH02 sensor for example. On the other hand, never do this to OLED display :) Mine started to smoke like crazy, and I only connected it for a second or two. Same goes for DS1308 RTC chip..
Check out my hand made open source Xronos Alarm Clock!
http://www.xronosclock.com

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6007
  • Country: us
    • LowPowerLab
Re: Can RFM69 survive 5V temporary?
« Reply #5 on: January 09, 2015, 01:51:25 PM »
An ISP programmer should NEVER supply the target with voltage/current. It should only read the voltage of the target.

Lensdigital

  • Full Member
  • ***
  • Posts: 151
    • Xronos Clock
Re: Can RFM69 survive 5V temporary?
« Reply #6 on: January 09, 2015, 01:57:47 PM »
An ISP programmer should NEVER supply the target with voltage/current. It should only read the voltage of the target.
Why? :)
Check out my hand made open source Xronos Alarm Clock!
http://www.xronosclock.com

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6007
  • Country: us
    • LowPowerLab
Re: Can RFM69 survive 5V temporary?
« Reply #7 on: January 09, 2015, 02:40:33 PM »
What is the function of the programmer? To supply power? Or do you see that as an "extra" feature cool to have?
Think for a second. How much power can an ISP programmer supply? 1A? 5A? What if your board uses 20A of power? Can it supply that? What if your target works at 3.3V? or 5V? or 2.8V? or 1.8V? Can a programmer meet those expectations? What's the job of the programmer? Power your board? Why not have programmers attached permanently to all projects if they act as power supplies? Wouldn't that be cool?

Lensdigital

  • Full Member
  • ***
  • Posts: 151
    • Xronos Clock
Re: Can RFM69 survive 5V temporary?
« Reply #8 on: January 09, 2015, 03:38:13 PM »
I see your point. Yeah it's a convenience for sure, why not use it if it's there? For most cases I'm ok with my USBTinyISP V2 supplying 5V, but I can remove jumper that enables that...
Why not have programmers attached permanently to all projects if they act as power supplies? Wouldn't that be cool?
Hmmm, Moteino-USB?    Ok it doesn't have ISP programmer, but you still program it via serial chip that's onboard, and provides power via USB  ;D
Check out my hand made open source Xronos Alarm Clock!
http://www.xronosclock.com

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6007
  • Country: us
    • LowPowerLab
Re: Can RFM69 survive 5V temporary?
« Reply #9 on: January 09, 2015, 04:40:59 PM »
We're talking about ISP in serial programmers. Not about USB-to-serial converters, which the FTDI chip onboard MoteinoUSB really is, and not a true programmer, it only provides a way for you to talk to the bootloader on the atmega so you would not need a true programmer every time you want to change the firmware.
And FYI the Moteino USB is not powered by the FTDI chip, but straight from the USB connector.

Lensdigital

  • Full Member
  • ***
  • Posts: 151
    • Xronos Clock
Re: Can RFM69 survive 5V temporary?
« Reply #10 on: January 09, 2015, 04:54:39 PM »
And FYI the Moteino USB is not powered by the FTDI chip, but straight from the USB connector.
I knew that  ;)
Check out my hand made open source Xronos Alarm Clock!
http://www.xronosclock.com