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Electronic circuit for solenoid

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: rp181 » Sat Aug 30, 2008 11:01 am

im gonna have to look into that.
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Unread postAuthor: jimmy101 » Sat Aug 30, 2008 12:54 pm

rp181 wrote:im gonna have to look into that.

You might want to look at Barry's truely excellent RLC simulator. All of Barry's coil gun pages are excellent.
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Unread postAuthor: rp181 » Sat Aug 30, 2008 3:13 pm

i have alot. Still trying to design a coil that will produce little ringing with 15ft max of 12 AWG wire, all the while meeting the reqs for the SCR.
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Unread postAuthor: Acdcmonkey1991 » Sat Aug 30, 2008 10:31 pm

So you are saying that I need some 555 cicruit or something where could I get all the stuff needed to make the board?
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Unread postAuthor: rp181 » Sun Aug 31, 2008 10:33 am

you need:
A mosfet, capble of atleast 20A (raiting goes down as pulse rate goes up)
a 555 timer
support resistors
pot to adjust frequency
a capacitor to set frequency
other support equip.

Search 555 timer, theres abunch of info.
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Unread postAuthor: jimmy101 » Sun Aug 31, 2008 12:39 pm

rp181 wrote:i have alot. Still trying to design a coil that will produce little ringing with 15ft max of 12 AWG wire, all the while meeting the reqs for the SCR.

If you put a high power diode, reverse biased, across the coil then you don't have to worry about ringing in the RLC circuit.

In my design based (stolen) from Barry's, there is a high power diode included in the the "hockey puck" SCR.
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The RLC circuit can't ring.
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Unread postAuthor: jimmy101 » Sun Aug 31, 2008 12:56 pm

Acdcmonkey1991 wrote:So you are saying that I need some 555 cicruit or something where could I get all the stuff needed to make the board?

RadioShack should have everything you need. If they don't have 555's you can use a 556 (two 555s in the same package). There are some advantages to using two 555's; you can use one to set the frequency (wired as an oscilator) and the second to set the duty cycle (wired as an astable or "one-shot"). There are ways to control both the frequency and duty cycle with a single 555 but it is often easier to do the two things seperately.

Like rp said, there are a bunch of websites that'll help you select the resistors and capacitors to get the 555(6) to do what you want. With a resistor or two and a sub-mini stereo plug you can plug the timer into the soundcard of a laptop and use the computer as an osciloscope to see exactly what the timer is doing.

LM556 Dual Precision Timer (14-Pin DIP) $1.99
Use an IC socket, don't solder directly to the IC.

Prototype + wire (this is very handy thing to have in your electroinics tool box)
Modular IC Breadboard Socket $7.99
Solderless Breadboard Jumper Wire Kit $6.49

Build final circuit on:
Universal Component PC Board with 780 Holes $3.49
Or, for a circuit this small perhaps:
Dual General-Purpose IC PC Board $2.49

You can also make your own circuit board with copper clad board, a laser printer, Chlorox Bleach and drug store hydrogen peroxide.
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Unread postAuthor: rp181 » Sun Aug 31, 2008 4:33 pm

put a LED in first to test it, way easier to debug if you cant use the comp o scope. Tell us if anything goes wrong. make sure the capacitor is correct polarity, thats a common mistake and will cause the led to stay on. You might want to put 2 pots, on for pulse length and one for duty cycle, it will asjust rate of fire and power of shot (longer pulse = more power to a limit)

jimmy: I have a diode (fast recovery 200A 1200v (5200A surge)) but by preventing ringing, pulse length will be shorter, and wont suckback as much.
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Unread postAuthor: Acdcmonkey1991 » Sun Aug 31, 2008 6:15 pm

I've got my radio shack cart all set up so could you please explain the circuit to me in english? I guess my question is how do i control the rate of fire? would the circuit look like this?
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Unread postAuthor: VH_man » Sun Aug 31, 2008 7:02 pm

i have a circuit from a book of mine that has an "astable" occilator that is EXACTLY what you want..... minus the MOFSET to control the solenoid off of the input. ill post it when my parents get off the computer with the scanner on it.......
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Unread postAuthor: rp181 » Sun Aug 31, 2008 8:10 pm

Let me explain how a 555 works:

it starts with feeding it current. The 555 charges the external capacitor until the capacitor is 2/3 of the voltage of Vcc (positive). It then discharges the capacitor. The resistor to the cap limit current, changing how long it takes to charge the capacitor, this is the off time. Once it reaches 2/3, then the capacitor is discharged through the discharge terminal. The resistor on that determines the on time (how long pin 3 gives out power). To change rate of fire: Say you want the valve open for 1/2 sec, and 5 sec between shots. For this, you would use a low value resistor connecting to discharge, and a high value to charge the capacitor. Another way to get a lower rate of fire is increase the capacitance of capacitor. 100uf is pretty much the lowest value you can see the blink with an LED on the output.

To see the rate of fire, use this calculator:
http://freespace.virgin.net/matt.waite/ ... /index.htm

The second one (the astable one) is the one you want

T1 would be how long the valve is open
T2 is time between shots
T total is a full on/off cycle (this is time between shots counting how long the solenoid is open use this for BPS)
Frequency is in hz, that means pulse a sec, 100hz will be 100 pulses a second.
Duty cycle is the ratio of off time to on time, a low duty cycle means less break between the on time, 50% would be equal on time and off time.


Monostable is a triggered 555. If you ground pin 4, then by changing the values, you can determine how long the output stays high. This would be good for a fast trigger shooter, so it fires everytime you pull the trigger rather then hold the trigger. This lets you get a consistent valve open time.

Start with 1 555 circuit, add another if you want later, the other one lets you do this: fire 5 rounds, wait 2 sec, fire 5 round, wait etc..

Tell me if you have any questions.

BTW, i really dont get your diagram. If your getting a breadboard (the thing with abunch of holes) post a link to it and ile tell you what to hook up wear, breadboards are labled with grid corrdinets Eg 1xc is first column and 3 down.
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Unread postAuthor: VH_man » Sun Aug 31, 2008 8:50 pm

nevermind.......... rp181 gave you all the info you need to make a circuit 100X better than the one i was going to give you...... that and our scanners broken......

you know, the whole solenoid idea really is kinda starting to make me happy.......... (adds to thousands of other projects)
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Unread postAuthor: rp181 » Mon Sep 01, 2008 2:55 pm

i just built a ocilator, not for this but for a boost converter, but it does the same thing. Instead of a MOSFET you can use a IGBT. Use the STGW30NC60W IGBT from onsemiconductor, they sample this for free (even for regular people) This is the one i am using, and it works, it it switches 16v 3A without even getting hot.
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Unread postAuthor: Acdcmonkey1991 » Mon Sep 01, 2008 6:49 pm

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Unread postAuthor: rp181 » Mon Sep 01, 2008 9:51 pm

that one is fine, remember that the top and bottom power strips are NOT connected.

Wire Size: # 22 AWG preferred; component leads with diameters.01 -.033" (.25-.84mm) acceptable


Eaither buy jumper cables, or get some wire from home depot, its kinda hard to strip and bend them right distances though.
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