"Sip n Puff" Trigger Help Needed.

[hook848]

Hello,

I am a disabled hunter using a pull-type-tubular-solenoid activated by a "sip and puff" pressure switch to fire my rifle. I am using my 12 volt wheelchair battery as my power source.

I wired the pressure switch and solenoid directly to my battery and it worked great. That is until it fried the switch. So now I need some help.

Solenoid info:

I need 48 ounces of pull within a stroke of .125 to .25 inches.

How many amps will I need and how do I add resistance to reach that value? Here are links to the solenoid I have.

http://www.solenoidcity.com/solenoid/tubular/s-20-100p1.htm
http://www.solenoidcity.com/solenoid/tubular/s-20-100p2.htm

The pressure switch I have now is described below:

"MPL 500 switches are designed for low current and logic applications, such as LED indicators and solid state relays. Typically, a load of 10 to 20mA will ensure reliable switching."

http://www.pressureswitch.com/products500.html

Can I use this switch with some kind of relay or should I buy one that will handle the amps needed for the solenoid?

I hope this will make sense to someone. Any help would be greatly appreciated.

Hook

 

[gerty]

looks like you need to add some sort of interface between the pressure switch and solenoid since the switch is only good for 20ma and the solenoid draws about 830ma for a one second pulse. Probably the easiest thing to do is use a solid state relay like a Jameco pn:kf0602d ($9.95), which is good for 2amps. It can be turned on by the pressure switch with a few ma and will carry the load of the solenoid easly.

 

[hotwaterwizard]

Go to the Auto Parts Store and get a Fog Light Relay.
It handles about 20 amps. Hook it up like This Diagram I made up for you.

 

[gerty]

Wizard..don't you think the coil of the fog light relay will draw more than the 20ma the switch is rated at????

 

[hook848]

Thanks gerty and wizard.

I'm going to try the solid state relay. I looked at the fog light relay and think the amps will be too high.

Gerty, are you sure about that part number. I couldn't find it on Jameco's web site.

Thanks again.

 

[gerty]

Sorry!! I gave you the product #
pn: 172591cx
I checked the website and it's there...

 

[Oznog]

Does anyone else feel uncomfortable putting the deadly force of a firearm trigger behind a low pressure switch and a solenoid?

Be aware that a solenoid plunger is heavy (you've shown a large solenoid- nearly 1/2 lb overall!) and free-floating. If it is bumped or shaken hard enough, the inertia of the plunger's mass can be enough to push the trigger and fire the weapon. Disconnecting the battery will not help this.

A pressure switch can also be fooled by a number of things, most common is kinking the tube. Impact/vibration on the sensor has some potential to affect the output as well.

 

[hook848]

Does anyone else feel uncomfortable putting the deadly force of a firearm trigger behind a low pressure switch and a solenoid?

Be aware that a solenoid plunger is heavy (you've shown a large solenoid- nearly 1/2 lb overall!) and free-floating. If it is bumped or shaken hard enough, the inertia of the plunger's mass can be enough to push the trigger and fire the weapon. Disconnecting the battery will not help this.

A pressure switch can also be fooled by a number of things, most common is kinking the tube. Impact/vibration on the sensor has some potential to affect the output as well.

Thank you for your concern Oznog.

Rest assured that I am fully aware of the potential hazards you mentioned. My hunting partner is also aware and we both take firearm safety seriously.

The only time a cartridge is chambered in my rifle is when I'm facing the direction I intend to shoot. This goes at the gun range and in hunting situations. I do not move my wheelchair with the rifle attached. I hunt and shoot from a stationary position and my rifle is only loaded after I'm in a safe position.

Hook

 

[hook848]

I received the relay gerty recommended today.

https://www.jameco.com/webapp/wcs/s...&catalogId=10001&pa=172591CX&productId=123042

I was going to use a 9 volt battery to power my pressure switch and my 12 volt wheelchair battery for the solenoid. Can someone give me an idea of how to connect everything including the relay.

Thanks.

 

[Oznog]

1. You should not need 9v. The solid state relay can handle a 9V input, and the pressure switch mentions up to 240VAC. Should be fine!
2. The solenoid probably needs a diode in parallel with it, it will generate large negative voltages when it switches off. I do not have data on whether the SS Relay you have has a diode already built into it to absorb this surge.
3. The MP600 is the MP500 already interfaced with a relay. This is the ideal component you should be using, rather than wiring up new stuff. This is especially true for your sitution where you don't have experience doing such things. Even I would pay extra to go for it, everything's packaged up nicely, not a lot of loose wires, and guaranteed to work together.

 

[gerty]

All you need is: neg from wheelchair batt to both the relay and solenoid.
batt pos to trigger switch other side of swich to pos of relay.
batt pos to one side of relay contact, other relay contact to solenoid.
All the trigger does is actvate the relay, the relay then switches batt power to solenoid.
The relay can be mounted anywhere it's convient, and I would use some sort of 2 pin plug to be able to disconnect rifle from chair/electronics.

 

[hook848]

Thank You!

Thanks to everyone for the advice. I wasn't able to put it together personally but I did find some good help.

A guy built me a circuit board and mounted the pressure switch and a relay on it. Nice and clean and no guessing on my part.

H.