hanging emonTx3

I just bought a emonTx3 and start installing it. When i runs on 9 v AC it works fine. But When I remove jumper JP2 and power the emonTX3 on either batteries or usb (5V, 1Amp) it hangs after 1 to 4 transmissions. No blinking LED and nothing received.

Any suggestions?

Robert Wall's picture

Re: hanging emonTx3

If it fails after a few transmissions, that would indicate to me that the power supply is not capable of delivering the current required by the radio transmitter.

As the 9 V ac input uses one regulator (U$11, a MCP1754); and the USB 5 V and battery feed in at a common point but use a different one (U$8, a MCP1702T), I would suspect either a very low current/voltage is available from your batteries, or the 5 V USB supply is very noisy, or there's a problem with the MCP1702 regulator.

Are you using good batteries delivering at least 4.0 V? (i.e. I wouldn't like to guarantee operation with rechargeable cells.)

If it's possible, look at the voltage on the 3.3 V rail (Pin 2 of the terminal block - it's labelled on the underside of the PCB) and check that it remains steady when the LED flashes. If it dips at all, then that dip is most probably the reason for it hanging.

larsthiesson's picture

Re: hanging emonTx3

I am using new alkaline batteries. Measured 4,8 volt out of batteries.

Voltage at pin 2 is 3,3 volt. Occasional it dips to 3,29 but never more. Tried to change the 5V usb to the one that drives my emonbase and same problem. 

So it could be the MCP1702 regulator

I will try to contact support.

Robert Wall's picture

Re: hanging emonTx3

Yes, it does look like a manufacturing problem. An email to the shop is the best route, now that we've eliminated the obvious.

glyn.hudson's picture

Re: hanging emonTx3

Hi Lars,

Sorry to hear that there seems to be a problem with your emonTx. The voltage at pin 2 on the terminal block should be 3.3V, the MCP1702 is a 5V > 3.3V voltage regulator, the 3.29V you measured is within limits and should not cause an issue. We have received your support request, please send the unit back to us for replacement / bug fix. 

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