Remote control & batteries

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Hello,
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
Fabrizio
 
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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.
 
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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.

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

I remember the special kits you could get of a conductive coating you could use to retreat the pads... limited durability I found. Don't recall aluminium foil dots tbh.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


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

Try attaching pictures directly :)

"To add a photo, files or non standard files.

First click "go advanced" in the box below the "quick reply" message box. Doesn't matter if you decide half way through a message to do that, it carries it foward.

Then click "Manage attachements". Maximise the new Window so that you can see all the text.

Click browse in the first box at the top and find your picture. Repeat for any more pictures.
Click upload... a message appears "uploading"
When complete the files will show as being attached. Now click the small text that says "close this window"

The pictures should now be attached and when you submit your post they will appear.

Make sure your pics aren't too big, a couple of 100k is plenty, and many members object when they are massive and it alters the margins
It tells you in the attachments window what max sizes are allowed.


If you want to attach a file that has a non standard format for example excel, circuit simulation etc then try putting the files in a zipped folder and attaching that."
 
just a question, it could be a silly one as I am not an expert.
If a measure the resistance between the remote connections for the battery (without the battery and without pressing any button), shouldn't I measure an infinite resistance?
to my test resistance is about 250 kohm..
 
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Your measuring across the circuit which will read as a resistance. Just because it shouldn't draw any current, it doesn't mean it will read open circuit. There will be an electrolytic cap across the supply for one thing and the various semiconductor junctions will read too.

So its normal to read something.
 
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Looking at the pics... that board will wash. Use fairly hot water and a tiny drop of detergent and a soft brush. Rinse and dry with paper towel. If the big IC is in a socket ? Then carefully remove it and dry around the pins of the socket. The IC can be washed too to rid it of any contamination. Also wash the rubber keypad.
 
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I've found you can't beat water and detergent or foam cleaner and water. Don't be afraid of wetting it. Pour some detergent on the PCB, driop some water on it and use a soft brush. Then rinse well using the brush.

I've washed countless remotes and many many whole PCB's from TV's VCR etc etc. Just make sure its totally dry before you put the battery back. Put it on a radiator to dry.
 
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