?s on identifying a 555 timer chip

Here's one... If I had a circuit that made use of a 555 timer chip, but it was not marked in any way that I could identify as the markings or a 555, how could I confirm that it was indeed a 555 timer chip? Still working on wireless remote for automatic door opener that doesn't. I believe I have confirmed proper function in the three transistors, but it looks like the oscillator isn't doing its thing. Power to the antenna goes up when the switch is depresssed, but it doesn't come back down like it used to, back when it gave me a nice 10kHz square wave. Now I am wondering if the chip is a 555 timer that is for some reason malfunctioning...

Many thanks for any help.

Dave

Reply to
Dave
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"Reverse engineer" the circuit by checking continuity visually, 
and/or with an ohmmeter, in order to determine the paths of the 
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Reply to
John Fields

9 pins power supply positive to pin 8 negatve to pin 1 output from pin 3 or 5 (all the other pins are inputs of different types)

that seems unlikely.

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Reply to
Jasen Betts

Get the datasheet or application note, and compare a sample circuit with what you trace on the board. I'm not sure you can ever be absolutely certain, but if it matches, it is most likely a 555.

Michael

Reply to
Michael Black

Yeah, that's what I'm doing, but was hoping there might be some simpler method of confirming the chips identity. Will keep at it. Thanks...

Dave

Reply to
Dave

What seems unlikely? That the three transistors are functioning properly, or that the oscillator is malfunctioning? I'm curious...

Dave

Reply to
Dave

Hadn't thought of that. Thanks. Will look at the options. Much appreciated...

Dave

Reply to
Dave

Typo: 8 pins

a combination of a 555 and discrete transitors comprising a remote control.

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Reply to
Jasen Betts

Aah. Well, the device only sends a brief radio signal to the door opener, whereupon the door opener opens the door. Not really much of a remote, but it does the job needed.

And it does, so far, look like the chip is a 555, but I'm not through yet. I am just glad that if this chip is what I think it is, which is a CMOS 555, I can pick that up at the local Radio Shack. They do still carry that much.

D
Reply to
Dave

Though apparently not for much longer, elsewhere they seem to be doing a countdown as to how long the chain will last, according to some, the count is in days.

Of course, there was the period here when someone asked about a 555 that they'd be told to "use a PIC", so even something with only eight pins could be something vastly more complicated. That would allow a much more complicated signal.

Michael

Reply to
Michael Black

It's a good idea. A resistor and capacitor between pins x, y, and z, etc, is your standard 555 circuit. Presumably it's either an astable to generate a frequency, or a monostable to send a pulse that makes the transistors oscillate for a set time. 555 oscillator circuits tend to all look very similar so you could figure it out from that. Get a circuit for one, and see if the pins are connected to similar combinations of components.

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Reply to
greenaum

Typo, change 5 to 7

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ehsjr

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