YOADRIAN

I hope one of you guys can give me a hand. I am building this field box and ran into a snag in the wiring for the fuel pumps. In the pictures you can see i have three fuel cans and will have three pumps, one for each. the pics only shows two now but there will be a third. The power panel is being set up for a master on/off switch for each pump and a fuel and de-fuel momentary switch for each pump. One battery will be used for the pumps the other two batterys will run in series for a high tork starter. The picture with the wiring is how i have it now, with the orange circle(the green wires) being the issue. I assume the pump runs in reverse polarity to defuel but how do i wire that? electrical is not my strong point. Thanks for any help ahead of time.

huck1199

You can use a switch like this with polarity reversed on each side of the 'off' ' center position. See the link below


http://www.radioshack.com/product/index.jsp?productId=2062537

YOADRIAN

I wanted to stay away from toggle switches and go with the momentary switches but even with the that set up and off being center NEG, and the pumps having a pos & neg only how many would go to each side of the pump? The power panels are able to do it so there must be a way.

huck1199

The center position has no connections. Each sidewould be wired withoposite polarities. What you want is a 3 position with a momentary button. Hard to find.

gsoav8r

My Feedback: (6)

Hi,
Im no guru but I think I drew this right. The way I laid it out, your black momentary will run normal and the red will run reverse.
The diodes are needed just in case the two momentary switches get pushed at the same time accidently. Without the diode protection the switches would be fried if the two were pushed at the same time. I think it would be the same as if you laid a metal band accross both poles of a battery. You get an instant ground, noise and sparks.

Id have to do some research of my own to be able to spec a diode in this setup.

OK, scratch the diodes for now. I goofed on that. I think they should be there somewhere but Im not seeing where at the moment.
Maybe someone else with more knowledge than I will chime in with some ideas.

Cheers,
James

aerofly0610

use a DPSTmoment switch to get the negative back to the battery when its pushed,,, to avoid battery shorting


I added a circuit diagram.... I think I got it all connected right.....

YOADRIAN

Thanks guys, i will work with what you gave me so far and keep you posted. Really thanks for your time in drawing up those diagrams.

LSF2298

My Feedback: (4)

Just don't push both switches at once. Maximum smoke and not from the smoke oil!!

huck1199

If you really want themomentary push button I would use a slide switch to give you oposite polarities and the output of the slide switch then feeds a single push button. This is the way standard power panels work and is fail safe for shorting the battery. You can label the slide switch "in" and "Out".

Phlip

I'm with Huck and LSF. You DONOTwant to build what Aerofly drew. TOODANGEROUS. Accidently push two buttons at once and BOOM!

This is how it should work with a slide switch for direction and a momentary for on/off.

YOADRIAN

Huck and Phlip well noted. I want to thank aerofly because i think they provided answers to what i wanted with what i had in mind at the time, but as always there is another issue which you both pointed out, even if i know that i would never ever hit both buttons at the same time, there is the REMOTE chance that one day little billy will ask me to borrow gas while i am flying and i will say "SURE GO RIGHT AHEAD" and your Alert will be driven home the hard way. I am spending a lot of time on this box to make it run right and look really good. I guess its the Marine in me that needs it squared away lol. The switches and buttons where put for simple operation and LOOKS so if you think of switch designs or layouts that would look good in that type box, i have another one not drilled out yet that i can use. I would rather not use a slide switch, just do to my dislike of them, but i will go toggle type if thats my only choices, but I am open to all ideas. I have two power panels which i have in other flight boxes i could use, but i plan to give those away to some needy kids to get them started in the sport and i would only use the pump switch in them anyways. I will post more pictures of other things i did that work great in it like my retractable starter cord with high tork starter and yes it works great lol.

LSF2298

My Feedback: (4)

I took another look at this thinking maybe you could add diodes to prevent a short if you pressed both buttons. I couldn't figure that out but I did notice I had overlooked the 5A fuse in the line. This would blow if you pressed both buttons at once so it wouldn't be a smokey situation, you would just need to replace the fuse. Your installation intrigues me and if I get some time, I'll see if I can figure out how to do what you want.

gsoav8r

My Feedback: (6)

Hey Guys. Ive looked at this a few times now and I think the diode idea just doesnt pan out. The diodes would work on the positive wires but the negative wires are still vulnerable. So that basically makes all the diodes useless.
Definitly need the 5A fuse or use different switching.
Cheers.

aerofly0610

Im a computer geek not an electrical guru .  Most of my knowledge is from Electronics for dummies and playing around.  I agree that what he wants is silly, but I was trying to help him do what he wanted,,, that's why I added the fuse in there to prevent battery shorting when two circuits are closed.  The safest way is to not allow closing of more than one circuit at a time, I.E. the selector switch with a momentary on switch (plus its the simplest to wire!).  I tried putting diodes in there, but they wouldn't work because the flow of electrons goes back and forth between fill/unfill.  Thus the diodes would prevent one direction from working.  Example a check valve on your fueler hose... you could fill but not drain. That is why he needs separate circuits for each direction on each pump, hence all the wires and switches!!!  If he did close two circuits on the same pump he could short the pump and the battery and electrical shorting is not a good thing around fuel!!!

So I hope you can get it to work the way you wanted!

Phlip

I apologize for my seemingly harsh criticism.  Although I haven't had the time to really look at this problem this weekend, there is a good way to do this.

The best way to do what he wants is to route the circuits through NC (normally closed) contacts on the switch of the opposite direction, for example, have the power go through the NC contacts of the reverse switch, then through the NO (normally open) contacts of the forward switch for the forward pump current.  Conversely, the power for reverse would go through NC contacts on the forward switch.  That way, when both buttons are pushed, nothing can happen.

The problem may be finding momentary push button switches with both NO and NC contacts.  Again, I haven't had the time to do any searching or draw up the circuit.  Perhaps later ...

But the first circuit I showed you with the slide switch for direction is definitely the easiest way to wire the circuit.

YOADRIAN

Ok guys i think i have it. What i did was drop the on and off switches and replaced them with a DPDT Toggle (as suggested) that way you have to flip the toggle either way to operate the momentary switches and neither one live at the same time. Phlip, i myself do not think it came across that way, your idea was sound and well informed. It is funny how i was so focused on having the momentary switches for the safety feature of it that i did not see the danger prior to it and i for one thank you for it. This is what it looks like now. I want to thank you ALL for your help and i will post pictures as i go thru this build.