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100nf capacitor polarity check

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metiz

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Hello everyone

me and my friend are working on a mk160 circuit boar. it's a remote controll through cellular phone. the board is all but done but we're stuck on 2 capacitors and a ldr.

there's no markings on the capacitors or the ldr to determine polarity. How can I do this without testing equipement?

they're 100nf capacitors and there's "104." written across it wich could be used to determine + and -

Can anyone help with this?

oh yeah, the negative pole always needs to be pointed towards the large conductive path that covers most of the pcb right?

Thanks
 
Is this a kit you are building?

Generally speaking, you only need to observe polarity markings with electrolytic and tantalum capacitors, both of which are clearly marked on the component body.

Your "104" capacitors are quite likely to be ceramic disc capacitors, or some other form of capacitor (Polystyrene, Polypropylene, Mylar, etc) which won't be affected by polarity. They can be inserted into the PCB any way around.

Same goes for the LDR. This is just a Light-Dependant Resistor and can be inserted into a PCB just the same as a regular resistor.

HTH.

A link for your reference, with regard to capacitors:
Types of capacitor - Wikipedia, the free encyclopedia

Another for LDR's:
Photoresistor - Wikipedia, the free encyclopedia
 
What are you tapping into a cellphone for? IED?

Let's not jump to conclusions...I sincerely doubt that everyone with an interest in timing circuits, in the past, had connections to PIRA or such like.

Is anyone with a 'foreign-sounding' nick or username now subject to speculation as to their intentions?

Let the project Q & A develop before casting stones....
 
polarity on unmarked capacitors

The only instance where polarity might matter is when using film caps (polystyrene or polypropelene) as bypass capacitors. In which case it's best practice to use the side with the outside foil towards ground.

I've seen a few audio circuits start to oscilate spontaniously at ultrasonic and even in the low RF range, although this would generally indicate poor circuit layout and other problems.

Film caps intended for this application generally have polarity marked. At any rate, 104 would be a .1uf capacitor which would in most cases be a ceramic disc or monolythic. Polarity is irelevant in these...
 
Hey everyone

Thanks for all your replies. And no, I'm not "tapping" into a cellphone. the board will detect the light comming from the display of a mobile phone when it's called. this triggers a relay wich can be used to power on a pc, alowing remote acces.
 
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