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Old 10-26-2010, 12:07 AM   #31 (permalink)
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Hey spider, Have you tried to make one using the exact directions? I want to try this.
The pics I made of the step by step assembly is dukie's chip. Considering I had forgotten the pinout when I went back, I think it is pretty straight. I tested it with an LED circuit and timer chip input when I was done. I didn't have any trouble with solder heat (you can tell I wasn't very gentle). The most difficult part is making sure the wires don't touch when they are not supposed to, including when you stuff it all in the frame.

I made a diagram of the test circuit, I'll try to figure out where it went.

I still play with mine. The magnetic reed switch works as a disconnect for weeks in between. The circuit fires when it is first powered up, but there are some common timer tricks you could use if that bothers you.
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Old 10-26-2010, 12:24 AM   #32 (permalink)
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I'm a bit confused... if you wanted to run only semi why even use the LM556 chip? Why not just run battery -> resistor -> microswitch -> 3-way? I'm no electrical engineer so I have to be missing something.
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Old 10-26-2010, 12:31 AM   #33 (permalink)
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I'm a bit confused... if you wanted to run only semi why even use the LM556 chip? Why not just run battery -> resistor -> microswitch -> 3-way? I'm no electrical engineer so I have to be missing something.
The point was to make the classic valve "chuff-less". Without any kind of disconnect or timer, you can easily bounce or pull the trigger before the reg recharges the dump chamber.

You could use an R-C delay, but the timing would change with the voltage. The timer chip runs the same between 9.5 and 7.5 volts.

The pneumag by itself was plenty light on the trigger, but you could still trip up the valve.


****
12-15-12

Just an update. This machine is still running. I put another 500 rounds through it today. Back in may I had the on/off top o-ring (quad) give up. I changed it out with a spare that I had bought at the same time. It failed after getting on the field. All of my quads had gotten old and soft. I converted back over to a teflon top o-ring (longer pin) and it seems to be fine. I was a little worried about the life span of the SMC-70, but it has been good so far. I'm probably still under 20,000 rounds on it, but at least the shelf life has been good. However, I must have more than 30,000 rounds on the MPA3, since it received more use as a plain pneumag ram.

Also, my Robertsr grips are still looking good. I was a little concerned that the real rattlesnake skin might fade or something over time.

***

11-26-13

Still chugging (it's chuff-less). Put another 1000 through it a few weekends ago.

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Old 05-25-2013, 01:38 PM   #34 (permalink)
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I realize this is older thread but it is still quite relevant today.

I have designed an uneven spool valve for a different application and was wondering how this circuit would work at 5v? I have been running the valve with just a micro switch but it is wasting air because the human finger holds the valve open too long.

Thanks, Paul
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Old 05-25-2013, 10:28 PM   #35 (permalink)
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I realize this is older thread but it is still quite relevant today.

I have designed an uneven spool valve for a different application and was wondering how this circuit would work at 5v? I have been running the valve with just a micro switch but it is wasting air because the human finger holds the valve open too long.

Thanks, Paul
`I would expect the dwell to need to be turned up quite a bit. I've not had this circuit with less than 7 volts, as far as I know. The batteries get old before I can really drain one. One of the design cheats is that solenoids actually like higher voltages on short duty cycles (like 10 msecs out of 50 is a 20% duty cycle).. The induction of the solenoid may make it slower to open if its rated voltage is the same as the supply. My SMC70 is rated for 5 volts.

Also, the low duty cycle makes the number of shots less of a concern than total run time. If you are regulating down to 5 volts, that's probably not a problem.

You could breadboard it first. There's no capacitor here, so you could run the duty cycle up pretty high. It kind of depends on your load as well (the solenoid).
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Old 05-26-2013, 09:16 AM   #36 (permalink)
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SPIDER,

Thanks for the help. I have been running a rechargable pack because I had it and I was afraid of hurting the solenoid. The solenoid is rated for 5v like yours. I guess I should run it just the way you are.

Paul
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Old 05-26-2013, 11:35 AM   #37 (permalink)
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Old 05-26-2013, 12:12 PM   #38 (permalink)
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SPIDER,

Thanks for the help. I have been running a rechargable pack because I had it and I was afraid of hurting the solenoid. The solenoid is rated for 5v like yours. I guess I should run it just the way you are.

Paul
I used some 5v Lucas ledex solenoid data to see how the duty cycle works with voltage. If the duty cycle gets too high, the solenoid will over heat. I did that during a test but I didn't run it to destruction. At least with a 5v supply, you don't have to worry out having the output stuck on.

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Thanks for the reminder! I happen to have a case of paint with no place to go.
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Old 12-19-2013, 03:26 PM   #39 (permalink)
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Featured on Hackaday!

SMAC Mag: Spider’s Minimal Analog Control Paintball Gun
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Old 12-19-2013, 06:32 PM   #40 (permalink)
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W00t!

I need to get out to the in-laws barn for a video (sheet metal!). I'll test fire in my back yard, but I don't let anything "get up to speed".
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