switch circuit

T

Torq

New Member
I'm new so my terminology will be off.
I have a working 12v vehicle CB that I would like to make a modification to.
I'd like for it to scan through the 40 channels on it's own.
With no modifications, I press/release the channel-up button, to go one channel up.
With no modifications, I press/hold the channel-up button it will RAPIDLY go through the channels.

My thought is to have a circuit to close the two pins on the channel up button, maybe once a second. Allowing time to hear activity on the channel.
one pin is 1v, the other is 10v-10.5v (varies each time powered up).
I tried an RC circuit but I'm doing something wrong.
It either goes one channel up just once, or it RAPIDLY goes through the channels.
T = 1 s = 1kΩ x 1 uF
 
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I made the changes, but I'm not seeing the function I'm looking for.
I think the RC circuit is not enough, and maybe I need an oscillator?
I get one channel change with the RC each time I connect it, instead of multiple channel changes.
I will start looking at oscillator circuits.
 
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The easiest way is to use a 555 timer IC in monostable or astable mode. Alternatively, if you need flexibility, you could use a small microcontroller (like an Arduino Nano).
 
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Please post a schematic of your circuit. It doesn't have to be fancy, but it must show all signal and power connections. Be sure to include a unique reference designator for each component, connector, etc.

ak
 
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R1 is 9k, try changing C to 2.2uf so timeout is ~22ms
VCC should be 12v.

If that doesn't work, you might have to drive an analog switch, or a small relay, with the 555 timer.
 
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The circuit you show above is intended to provide a single long pulse each time the button is pressed; the values are daft though, it suits far longer delays than the button press time.


Try this version from the same site, and connect the button in series with the connection between VCC and Ra

If Ra is relatively small, eg. 1K, and Rb quite large, eg. 47k, the output will have almost symmetrical high & low times.

Try 47k and 10uF as a starting value? Or 100K if that is too fast.




ps. 9k1 is a standard resistor value, in the "E24" series; 24 value increments per decade.

E series of preferred numbers - Wikipedia

en.wikipedia.org
 
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Here, turn on S1 to start your pulse train at 1Hz (approx) and press S2 to get Hz or more (depending on capacitor C1 size. R3 can be replaced by a wire (0 ohm) connection (my iPad simulator doesn't like capacitors in parallel).. Note, S2 is normally closed.
 
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Torq said:
With no modifications, I press/release the channel-up button, to go one channel up.
With no modifications, I press/hold the channel-up button it will RAPIDLY go through the channels.
Click to expand...
Below is the LTspice sim of ZZO's basic circuit without the added timing capacitor:
I added a pull-down resistor to the RST (/R) input, which is required for proper reset operation, since a RST open is equal to RST high.

 
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