I am sure many of us have had or still have the little weather stations as sold by LIDL, Aldi and many many others.
I have had several over the years and almost all of them end up with inaccurate RH readings usually 20% in my case they have all had the HR202L sensor to measure humidity and this is what has failed. I just order new sensors and solder them in.
So one of my outside sensors started showing the dreaded 20% so I ordered 10 from China (£5 inc postage).
When they arrived in 7 days I was pleased, until I opened them and it was clear that they had not been fully etched as where the interlocking "fingers" of the sensor should be there was a grey blob. Hmm I thought perhaps a new design ?
So I stripped down the sensor unit, removed the old one and added a new one 95% straight away ! let it run all night but it was still between 92 and 95% and this tied up with un-etched grey blob conducting too much.
I removed "blobby" and powered up the sensor without any humidity chip 20% was displayed.
So 20% must represent "open circuit" and I decided to take a closer look at the old sensor. At the junction of the legs and sensor body there is a type of clamp to hold the leg in place which is then soldered to the sensor fingers for each side (picture). I noticed some white deposits at each solder joint rosin ? oxidation ? (if the legs were aluminium alloy).
I re-flowed the solder on each joint and now the old sensor works fine (binned the new ones). I then dug out two more old sensors and re-flowed them and now they work again !
I hope this observation might help someone else.
TC
ps I remove them so I could apply some pressure to the joint when re-flowing the solder ans I think this helped close the clamp as well
I have had several over the years and almost all of them end up with inaccurate RH readings usually 20% in my case they have all had the HR202L sensor to measure humidity and this is what has failed. I just order new sensors and solder them in.
So one of my outside sensors started showing the dreaded 20% so I ordered 10 from China (£5 inc postage).
When they arrived in 7 days I was pleased, until I opened them and it was clear that they had not been fully etched as where the interlocking "fingers" of the sensor should be there was a grey blob. Hmm I thought perhaps a new design ?
So I stripped down the sensor unit, removed the old one and added a new one 95% straight away ! let it run all night but it was still between 92 and 95% and this tied up with un-etched grey blob conducting too much.
I removed "blobby" and powered up the sensor without any humidity chip 20% was displayed.
So 20% must represent "open circuit" and I decided to take a closer look at the old sensor. At the junction of the legs and sensor body there is a type of clamp to hold the leg in place which is then soldered to the sensor fingers for each side (picture). I noticed some white deposits at each solder joint rosin ? oxidation ? (if the legs were aluminium alloy).
I re-flowed the solder on each joint and now the old sensor works fine (binned the new ones). I then dug out two more old sensors and re-flowed them and now they work again !
I hope this observation might help someone else.
TC
ps I remove them so I could apply some pressure to the joint when re-flowing the solder ans I think this helped close the clamp as well
Attachments
Last edited:
