555 timer circuit with variable cap and res

[bimm25e]

So Im going to be using a 555 timer to control a single "pop" of a recoil solenoid,

the solenoid is driven by a 24VDC power supply,  I assume I would need to run the circuit at a lower voltage and trigger a SSR at the output.

If I wanted to save some time could I use a variable capacitor and variable resistor, that would allow me to fine tune the length of the pop without buying a kit of random resistors and capacitors and continuously swapping them until i get the results I want.


This will all control off of a JAMMA button press, 1 press = 1 pop.  what voltage is moving through the buttons?  any reccommendations on good starting values for the cap/resistor and SSR ?

[lilshawn]

i don't know about all that...

it seems like you are over complicating a circuit with unusual parts that "simply" needs to have an equally complicated mosfet driven solution. 

I'll tell you why... A solid state relay is basically a low impedance mosfet switcher on the output side anyways. by using it in this manner you suggest, you may as well go straight to a MOSFET switcher using, say an IRL540 to drive your solenoid.

i would suggest using a 4N35 optocoupler to protect your jamma signal from the button. your board WILL NOT like 24 volts run into it if anything fails. it's output can be tied to your circuit trigger easily.

you can easily build an adjustable 555 timer solution:



you'd just have to modify this circuit to "one shot" your timer circuit instead of being astable.

i'd recommend building a small circuit to control an led or small lamp first. then work your way up.

[rhys]

I could probably build a breadboard Attiny with a trimpot and SSR, and write code to do this in under an hour if I had the parts on hand.  An interrupt triggered by the button activates the SSR and holds for a duration set by the trimpot value then releases.  Make the loop atomic and it won't allow the ISR to be triggered again until the loop completes.

Pretty simple MCU application....  But I know MCUs, I'm not so great with analog circuits.

[ed12]

pin 6 is the trigger voltage hence it is a elecrtolytic
u s the charge is held by this cap for xx time which s fixed by it value

ie 1mf is short 10mf is long
the pot is the depeletion part
turn 1 way for longer the other for shorter

ie the time it takes to deplete the charge on the electroltic

ed