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sattwa 11th January 2013 07:17 AM

Remote control & batteries
I am writing to ask some advice on a remote control that i bought second hand and that tends to make life of battery quite short (it's one 9V battery). I cannot measure any current in a tester put in series with the battery when no button is pressed (only about 0.10 mA when any button is pressed).
What the problem could be? any thought?
Thank you

Mooly 11th January 2013 08:15 AM

Are you 100% sure on your meter readings ? Test the meter with a resistor and the 9 volt battery. A 100K resistor should draw around 0.09 milliamps.

Most remotes should have NO measurable current draw when not transmitting.

Are you sure the batteries are running down and that its not the act of physically replacing them that gets the remote working again indicating a connection issue or intermitent problem on the PCB.

wintermute 11th January 2013 08:30 AM

I started to answer this but my machine crashed :rolleyes: I'm with Mooly, something doesn't add up. What sort of batteries are you using? Alkaline?

A typical Alkaline 9V battery (according to wikipedia) is around 500mAH capacity if your current draw when pressing a button is only 0.1mA then even if the button was held down continuously it should last around 5000 hours! That is 208 days.....

if you are using rechargable NimH (or worse, NiCd) batteries then if they are not the newer low drain type then even if they are not in use then I would expect them to be flat within a month.

As Mooly said though the contacts could be the problem. I have a remote that often I need to pull the batteries out of and put back in to get it working. They test fine on the multimeter and it works fine again once they are put back in.


sattwa 11th January 2013 08:54 AM

Thank you very much for your reply. The batteries I am using are alkaline and the meter (a Fluke 177) seems to work fine (I tested a 220k resistor and the measure is fine). The battery that I removed tests about 1 V, the new one 9.93 V)

madtecchy 11th January 2013 08:59 AM

Are you using a known brand battery. Or the ones from a thrift shop.. Remote controls two common faults Bad connection between contacts on remote and where they are soldered to the pcb.. The other a dry joint on the ceramic resonator..

Regards Mark

Mooly 11th January 2013 09:04 AM

Its possible that the remote is suddenly doing something strange and locking up drawing current. Has it a ceramic resonator. The legs on these often fracture. Whether that might cause a problem I don't know.

What I would do is dismantle it and look carefully for any possible physical problems such as battery wires that might short etc. Is the battery clip OK, I'm thinking of those with flying leads. If they were intermitent could it "spike" the uP and cause a lock up drawing power.

Next up I would wash the PCB and keypad (assuming its a normal type and not a glass screen touch one) and the conductive rubber keypad. Done that thousands of times.

Beyond that and its anyones guess.

Mooly 11th January 2013 09:04 AM

Lol :D Ceramic resonator.

sattwa 11th January 2013 09:06 AM

this is what I used in only few months:
Tesco, Ikea, Sony (from chinese shop), Energizer (4 euros)
the last one lasted longer, but still only 2-3 months :(
the battery comes out empty so it should not be a problem related to bad connections..

madtecchy 11th January 2013 09:09 AM

Hi Mooly LoL. Ever remember those little sticky dots of aluminium foil that could be stuck to the rubber contacts whos resistance had increased ..

sattwa 11th January 2013 09:21 AM

this is what the PCB looks like
it seems fine to me, connections to the battery are quite solid and there are no traces of rust, anyway I will clean it with some isopropanole

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