Recoil generator for toy gun?

[dknguyen]

Yup

An electrolitic... wow. I can't believe you just think of things like this.

Standard bypassing practices for electric motors Don't forget to use it on your ICs (maybe tantalum capacitors, not electrolytic).

 

[Nigel Goodwin]

Standard bypassing practices for electric motors .

Except it's not use for bypassing, it's used to store the energy to move the solenoid - the same technique is used in remote controls, a large electrolytic is used to store the energy for the high current pulses to the IR LED. Without it the batteries become useless VERY quickly, only lasting a week or two instead of a year!.

 

[dknguyen]

Bypasing

I have always thought about capacitors using parallel capacitors for noise-filtering and votlage-spike-filtering as the same thing, except one is at high frequencies and one is at lower frequencies (or is that a false assumption that voltage spikes have lower frequencies than noise?

Should I have said decoupling instead of bypass in my last post? Are you saying saying decoupling capacitor implies a different purpose than bypass capacitor.

The more I think about it the more I think that bypass refers to allowing noise to bypass the rest of the circuit to ground while decoupling refers to "decoupling" the motor from the battery to dampen voltage spikes. Or are bypass caps a subgroup of decoupling caps?

Are noise caps and voltage-spike caps taking advantage of different characteristics of the capacitor? Noise caps use the transfer function of the capacitor for it's high-frequency passing characteristics and voltage spike caps use for their large energy storage and fast response to act as a "secondary" battery? Or are they all taking advantage of the same capacitor characteristics but at different frequencies ranges?

 

[Electric Rain]

So do you guys think a 10000uF cap is overkill?

 

[dknguyen]

Yes

Yes, that capacitor is absolutely majorly humongous, a whopping 10mF. (You know how large 1F is right? that's why most caps you see are in the pF range and usually top out at around the uF range) I would think 2200uF would be excessive already, especially at 2A. However, I also think it depends on how fast your battery can react to the changes in current demand. Use it if you want though...I don't think it could hurt.

 

[Electric Rain]

I just want to make sure it's big enough to supply a nice surge. If you think a 2200uF cap would work though, then I'll go with that... they're cheaper.

 

[dknguyen]

For comparison sakes, a 2200uF capacitor is used in my 40V, 20A motor controller for decoupling.

 

[Electric Rain]

Oh, well... there you go then. I guess that will work fine.

 

[Nigel Goodwin]

Should I have said decoupling instead of bypass in my last post? Are you saying saying decoupling capacitor implies a different purpose than bypass capacitor.

It's not really either, it's purely for energy storage, the battery charges the capacitor - then when the solenoid fires the energy required is drawn from the capacitor, and NOT from the battery. As a battery loses it's charge it's internal impedance increases, eventually it won't be able to supply enough current to fire the solenoid. However, as it has a considerable amount of time to charge the capacitor, it can do this even with increased internal resistance.

It also allows you to use far smaller batteries, as I mentioned before, remote controls work like this - and if the capacitor goes O/C (or more commonly dry jointed), the batteries only last a couple of weeks and are then too weak to work anymore.

 

[Someone Electro]

Well you could make a DC to DC converter and charge that cap up to the 50V and discharge that the higher voltage will push more curent trough it and a more instetanius shock. The cap you stated can hold 12 joules of energy.So if you charge 3 of them in parallel then it should give quite a pulse.But then you also have to think of charging .To charge 3 of those caps in half a second you need 72 Wats of power input.But then agen sesonoids are prety eficent so a large portion of that power is gona be thurned in to the recoil.

I dont know if the sesonoid can take such pulses feq whithout overheating.When pulsing caps a lot of curent is created and lot of curent means more heating.

 

[Nigel Goodwin]

I think you're getting rather carried away now! - he's wanting a realistic 'kick' as you fire the gun, not wanting to fling it out of the users hands!.

Obviously the thing to do is try different solenoids, supplies, and capacitors, to see what gives the required effect.

 

[Someone Electro]

Well he asked for a strong recoil