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Hello this is my first post so please be gentle.

Im looking to build a multivibrator circuit that pulses a light at 0.08sec intervals 3 times, at which point i want the light to stop pulsing untill the button is pushed again essentially reset the circuit.

Im figuring that i could use a pulse counter to detect the fast pulses and on the 3rd pulse turn off the multivibrator circuit untill the switch on the vibrator circuit is pushed again.

Basically im trying to flash super bright leds in a muzzle flash simulator for a theatrical effect. i want to use a selector switch (3 settings) semi/3 shot burst/full auto the semi will just be the switch hard wired to the led, pull trigger and led flashes, the selector switch on 3 shot burst is the tricky bit!! and the full auto i have figured out.
the 0.08 sec is quite important to get right between flashes and the "3 shot burst" is also just as important.

Is there a way to make a pulse circuit that i can get each pulse .08 sec apart? could i use a 555 with a small resistor and cap??

any ideas??

im new to electronics, i understand the basics and i know what components do etc

thanks
simon

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To make a burst of three flashes you will need two timer ICs, one wired as a monostable and the second as an astable MVV.

Timing must be accurate enough to have the astable put out three pulses until the monstable times out and keeps the astable in reset condition.

At 80ms pulses and  50% duty cycle the 'on-time' of the monostable must be 400ms, after which the monostable resets the astable.

Initial triggering is done by taking the TR input of the monostable to ground via a pushbutton. (Pulse must be very short or use a non-retriggerable circuit)

Check out the timing diagram in the attachment.

HtG

post-23108-14279143954506_thumb.gif

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hey herman
i have some rather silly questions about components that i only recent discovered i lacked knowledge of.
capacitors, when it comes to voltage ie: 220n is it a 200v or a 50v? and what determines the voltage within a circuit? also the variation of farads in the circuit you helped me with are of very different voltages this also is difficult for me to work out, i looked on the web for answers so that imi not being dumb, i guess i just needed to ask as im not sure what caps to get.

thanks HTG i hate to ask these childish questions, but they have to be asked sometimes :)

simon

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capacitors, when it comes to voltage ie: 220n is it a 200v or a 50v? and what determines the voltage within a circuit?
simon




200n is 200 nanofarad.  Caps are general valued in microfarad (uF) for the largest through picofarad (pF) to nanofarad (nF)

The voltage of a cap is the largest voltage the cap is capable of carrying.

Think of caps in circuit as small batteries that charge up to the voltage in the circuit,  then release that voltage as the circuit demands (timing, etc.)

I'm sure you know that caps will not directly pass DC current and are therefore used to block dc from certain parts of a circuit.

Hope this helps.
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thanks htg,
the nf, pf, and uf i figured out (wikipedia is great) but now im guessing again the voltage of the caps depends on the requirement of max voltage of the circuit, ie: 240v a/c requires higher caps and a small 6vdc circuit using a 50v cap.

why was the previouse posts deleted?

my email is [email protected] i would love the pcb123 file i downloaded the programme, thanks htg, i dont mind my email on here as its on my profile publicly displayed.

simon

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Hi Simon,

I don't know the reason why some of my posts were deleted. I guess it's a simple data base error, since none the posts was abusing or aggressive. I did the design using Eagle (not 123 PCB). You might download a free version (Eagle light) from http://www.cadsoft.de.

Eagle light is limited to a max. board size of 100X80mm and two layers (full professional version:800X800mm and 16 layers)

You might want to play with the layout to make fit your needs. The board size is well within limits.

Just don't care for the voltage rating of multilayer capacitors. They are rated starting at 63V and step up to 2.5KV. Using a 63V (small footprint of 1/10") types you will always be within limits applying those for low voltage circuits.

You should take care of the appropriate voltage rating of electrolytic caps, starting at 10V up to 385V. For a supply voltage of 12V use caps rated 16 or 25V.

Hi allvol,

nobody is perfect.  ;D

I assume you know about capacitances well, the mixup was probably caused by a power fluctuation in the brains.  ;)

However, you just should make sure to post correct statements here. A newcomer might take a wrong statement for the truth and try to sell it as a "religion".  ;D

Both of you, have a nice day.

Regards

HtG

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