Verify power draw of Wemos D1 Mini Pro after getting wet under power

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oserror
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Verify power draw of Wemos D1 Mini Pro after getting wet under power

Post by oserror » Thu Sep 12, 2019 4:14 pm

I made a small weather station using a 18650 Lithium battery, a small solar panel, a TP4056, a BME280 and a Wemos D1 Mini Pro. Everything was working fine until a bad storm, when the device fell onto my deck and the rain was on it for a couple of days. I was away and came back to the device not working.

I used a bag of silica desiccants to dry the board out, and afterwards I got the circuit to work for a couple of hours until a crash. The day was sunny and the TP4056 light was on indicating it was charging. However, the battery voltage kept dropping, which was not the case before the rain event. It seems to me that the sleep mode was drawing more current that usual. The code had the Wemos powering on for about 15 seconds to record and send the data, and then to sleep for 10 minutes, repeating the cycle.

How can I determine if the Wemos is any good? That is, can I measure the power draw with a multimeter, jumper wires and a bread board? And also the tp4056?

I have all of the parts to make a new board but I wonder if I can at least salvage the Wemos. The soldering procedure to use the external antenna isn't easy for me to do with a new Wemos.

Thanks!

EDIT: Maybe this is off-topic for this forum. If so, can anyone point me in the direction of a better place to pose my question?

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jimmo
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Re: Verify power draw of Wemos D1 Mini Pro after getting wet under power

Post by jimmo » Mon Sep 16, 2019 6:06 am

You can measure the current draw with a multimeter... it can be a bit annoying though because the sleep current will likely be in a different range to the wake current. You can work out power from this because the voltage is (hopefully) constant.

Other than the desiccant, did you do anything else to clean the boards?

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oserror
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Re: Verify power draw of Wemos D1 Mini Pro after getting wet under power

Post by oserror » Mon Sep 16, 2019 3:54 pm

jimmo wrote:
Mon Sep 16, 2019 6:06 am
Other than the desiccant, did you do anything else to clean the boards?
No, I didn't. I'm a novice with electronics. The TP4056 is, unfortunately, securely fastened to the board and I don't think I have enough skill to desolder it. I do have about 10 copies of the main board and enough parts to make another one.

I managed to check the Wemos by putting my multimeter in series. I tried a number of ways and finally put the multimeter between the source power and the Wemos. I know it's probably elementary to many on this list -- I'm just glad I figured it out. I did verify that the device is going to sleep; the current dropped to about 2 mA from around 76 mA (I believe this was the value). So I think that the Wemos may be salvageable. If not, I'll replace it.

What would you suggest I clean the old board with?

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jimmo
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Re: Verify power draw of Wemos D1 Mini Pro after getting wet under power

Post by jimmo » Mon Sep 16, 2019 11:11 pm

I'd probably use isopropyl alcohol. It's pretty gentle, easy to buy, and safe to use.

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