2.27V instead of the 3.3 on Moteino USB when connected to USB

VdesmedT · April 17, 2015, 02:09:23 PM

Hi,

One of my moteino USB is only delivering 2.27V from both VIN and 3.3 pins.

Does anyone has a similar experience or could suggest a test to identify the problem ?

Thanks

Felix · April 17, 2015, 03:22:50 PM

Did you wire it up in any other way than to the USB before this happened?

VdesmedT · April 17, 2015, 04:35:23 PM

I use on a breadboard to test 9V battery voltage measurement... I start to understand my mistake

Did I burned the voltage regulator ? Can I replace it ? Or is it the ftid itself ?

Felix · April 17, 2015, 09:47:25 PM

You may have burned the regulator.
It can be replaced with a MCP1703 3.3V regulator.
I can do it for you if you're willing to ship it back and pay for the return postage.

VdesmedT · April 18, 2015, 04:30:53 AM

Thanks for your support Felix.

SOT-23 right ?

I will give a shot myself as shipping from Europe-Belgium will cost the price of a new moteino but tank you for the part number. Have you ever considered having a representation oversea ? Would that make sense ?

Felix · April 23, 2015, 10:00:57 PM

Yes the Part is SOT23-3 MCP1703-3.3V regulator.
There are a few distributors now in UK and Spain, possibly more coming.

VdesmedT · May 26, 2015, 04:58:50 AM

Hey Felix,

I finally got my hand on a MCP1703 3.3V and replace the one on the moteino USB... same result : when connected to USB, both VIN and VOUT got to 2.2V. Is it possible that I damaged the new regulator by applying to much heat during soldering (i don't know how sensitive are those guys but 5 sec at 300C were enough to finish the job).

Could it be that another component produce that effect ?

thanks.

Felix · May 26, 2015, 07:34:36 AM

Possible? Maybe. It's really hard to say or guess without analyzing the actual unit in question.
I would be curious what happens if you apply 5V to the regulator on a breadboard (solder wires to the SOT23) and see what the output is.

rdww60 · May 26, 2015, 03:36:44 PM

Quote from: VdesmedT on May 26, 2015, 04:58:50 AM
Hey Felix,

I finally got my hand on a MCP1703 3.3V and replace the one on the moteino USB... same result : when connected to USB, both VIN and VOUT got to 2.2V. Is it possible that I damaged the new regulator by applying to much heat during soldering (i don't know how sensitive are those guys but 5 sec at 300C were enough to finish the job).

Could it be that another component produce that effect ?

thanks.

Depending on what type of equipment you have...

1) Try unsoldering pin 2 of the MCP1703 and lifting it up from the board, plug in the USB and see if you get 3.3V on the lifted pin 2 leg. If yes, then
do the LEDs on the FT232 light up when you try to program? If the FT232 LEDs do light up, then something downstream as you suspected is causing an issue.

2) Try temporarily replacing the Shottky diode with a simple 1N914 or similar, Anode to VBUS. If the Shottky is bad, this will at least allow the regulator to show 3.3V on the regulator output (with pin 2 lifted)

I wouldn't think a bad capacitor would stop at 2.2V, it would likely take you all the way to Gnd.
Short of that, it means that one or more of the Flash, Radio, or Atmega has been damaged.

VdesmedT · May 26, 2015, 05:26:20 PM

Hey there,

I wired up the original MCP1703 to a 3.7V LIPO battery and measured 3.74 between GND and VIN and 2.11 between GND and VOUT. Then I wired up one of the brand new MCP and measured exactly the same thing.... I start thinking that perhaps I damaged the MCP's by soldering them. I use a Weller WXMP set at 250C and it does not take more than 2-3 sec per pin...

Thanks rdww60, I saw your post too late and I desoldered the MCP already. Seems I do have a regulator issue at the end but maybe also an equipment issue (dead brain maybe :-))