I am assuming that an alkaline battery will not have enough current to run the solenoid with enough kick. Estimate 1 amp is needed to fully actuate the solenoid. Max discharge rate of 9V batteries is much less so I will need a capacitor to supplement the current supplied.
1 farad = 1 amp second at 1 volt
F=(A*S)/V
Farad=(Amp*Sec)/Volt
AA battery holds 2.8 amp hours at 1.2V
Equivilant capacitor is (2.8*3600)/1.2=8400 F
For the solenoid, estimating 1 amp discharged over 100ms. That is 0.1 amp seconds at 12V
(0.1)/12=0.00833333
8mF (8000uF), that is a large capacitor, give another 1.5 for tolerance and we get 12000uF
Wow, I found a 36V 12000uF capacitor for $3. It has a 1inch diameter.
Now that I have the discharge rate I need to figure out the charging rate before the next time I can fire the solenoid.
The solenoid coil has a resistance of 4 ohms. The capacitor will completely discharge across this load in 35ms.
http://hyperphysics.phy-astr.gsu.edu/HB ... apdis.html
Alkaline batteries can deliver ~700mA without exploding.
This means their internal resistance is around 1.7 ohms. Directly connecting our 12000uF capacitor to the alkaline batteries will give us a duration of 90ms to reach 99% charged.http://hyperphysics.phy-astr.gsu.edu/HB ... hg.html#c2
Total charging plus discharge time is 125ms. The max fire rate is 8/second or 480/minute. Kinda want to be able to do 600/min or 10/sec so I can use the solenoid for a prop halo assault rifle. Have to recalculate.
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Also need to take into account that the solenoid has a 10% max duty cycle. 35ms on and 90ms off. Duty cycle is 28%. This just means that the solenoid will heat up a bit during use. Take some caution anyway and pad the off time up to 315ms. That will give us the 10% duty cycle. Also decreases the max fire rate to 171/minute.
I could also change the on time cycle. I don't even know if the solenoid can actuate as fast as 35ms, but I guess I'll find out.
