EmonGLCD - input voltage from USB

Does anyone know the min and max input voltages for the USB connection on the emonGLCD. 

Iv got a 6v solar to lipopack charger, Its also got an output but it does not seem to be regulated. Eg when the solar panel is in sun the output from the board can get as high as 6.0volts 

It does seem to boost the voltage of the lipo pack to 5v when no solar but dont want to blowup the glcd.

Link to solar to lipocharger.



jstoaks's picture

Re: EmonGLCD - input voltage from USB

I would double check your connections, That should not be. I have the exact same device from Lady Ada with her 6V 3.2 Watt Solar Panel. It is powering my Emon setup that I have built. Check my site http://www.stoaks.net for a couple of pics I posted recently.

I believe the MCP1702 voltage regulator onboard the EmonTX PCB can take up to 12-13 volts input.

The adafruit solar panel and charger setup is designed for 3.7 volt Lipo Batteries, You will see no more than 4.2 volts at full battery charge or full solar capacity coming from the load side of the Solar charger. The panel itself is designed for max 6 volt output closed circuit.

The MCP73871 on the solar charger has a max input of 7 volts.

Check the datasheets for both of these and you will find all the details.

Once you can get the correct voltage from the solar charger, Run it to the input side of the 3.3 volt regulator onboard the EmonTX PCB. The regulator is a Low Drop Out, meaning it can handle regulating voltages that are just above 3.3 volts. 



robw's picture

Re: EmonGLCD - input voltage from USB

Iv also go tthe 6v 3W solar panel and defiantly when you connect a voltmeter to the output you get 5.2v with no solar pannel and between 5.5 and 6.4 with the panel in light.

The battery is a 2700mah 3.7v cell. Just check with a multi meter and its voltage across it is 5.2v on a 3.7v cell.. WTF

These voltages were taken with no load so maybe it drops under load i don't know,

any ideas as i really don't want to blow up a GLCD unit.

Your site was kinda of push to try to get the GLCD unit portable. 
Iv redesigned the case for it so its got two contacts at the bottom that the solar connects to but its like a drop in the cradle wireless phone one.

glyn.hudson's picture

Re: EmonGLCD - input voltage from USB

I would recommend not powering the emonGLCD with higher than 5V. The emonGLCD does have an MCP1702 voltage regulator on board but the display is powered directly from the 5V input, connecting higher than 5V would probable damage the display. This will be fixed in the next version. 

Also in the next version of the emonGLCD I would like to include an Li-Po battery charger IC (MAX155) and a Li-po battery socket for full battery wireless operation. I agree there are many occasions where it would be nice to have to option to move the display about. 

robw's picture

Re: EmonGLCD - input voltage from USB

Looks like my digital Voltmeter just needed a new battery..  Tested now and reads 4.5V fully charged.. DOH.. Have tested it and works fine connected to the USB port.. not tried the 3.3v line as its too high for that i think also need to power the screen so USB i think only..

Glyn Are the wood laser cut files available to mod also. Would love to try to mod mine to fit the charger + battery in the wood bit behind + make the front slightly bigger so it covers the the lcd back light to the left as you look at it.


glyn.hudson's picture

Re: EmonGLCD - input voltage from USB

The CAD designs are up on thingiverse: http://www.thingiverse.com/thing:22295

We don't usual sell just the fascia kit on it's own but if you would like this the cost will be £8. Just purchase 8 x 'customized order payment' option http://shop.openenergymonitor.com/special/ and leave a note at checkout. 

It would be cool if you posted up some photos of your modifications. Maybe we could start a 'show off your emonGLCD mods' galley :-)

All the best, 


robw's picture

Re: EmonGLCD - input voltage from USB

Thanks Glyn

See pics below.

Like a muppet i extended the wrong side so have had to flip the front (reason it does not say openenergymonitor.org etc). Was hiding the buttons . Also its 3mm not 2.5mm so non of the screws fit. DOH. .  Screw holes for the lipo charger are too small. Oh well Anyway there are some areas that need to be sorted before its done. And im sure i will be using works laser cutter a few more times also.. 

Making a stand for the solar panel like a dock so the GLCD unit will have two prongs under it to connect the solar panel base. 

Will post more when done.

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