Project: Remote Live Trap --- Momentary switch / Micro 3VDC to 12vdc - .34A (@3v) Push/Pull Solenoid (14.7ohm internal resistance) / Capacitor Power Source

I'm using a momentary switch trip plate and it may have the switch depressed for long periods. Not good for the push/pull solenoid I'm using! 5 sec duty cycle. That's why I'm looking at using some type of depleted power source after one push.

I'm thinking a capacitor might work to provide power for a one time operation? I'll reset the circuit by charging the capacitor with a battery pack. If there is an alternative power method I'm open to any change.

I've done a little research on capacitors but I'm getting confused in choosing a capacitor and calculating the circuits resistance draw. And choosing one that will hold the charge for at least 2 to 4 days and also match the solenoid power requirements?

Thanks for any help.

 

It’s not easy to calculate, as it depends on the mechanical load on the solenoid, its inertia and its frictional loss.
It also depends on how long you need to solenoid to remain its is activated state.
My suggestion would be to try 4700uF and see if it works.

I would also recommend using a monostable such as a 74HC123 and a power transistor. It does add more complexity to your circuit, but it makes the activation time easy to adjust, and it reduces wear on the switch due to sparking caused by the solenoid’s inductance.

 

It’s not easy to calculate, as it depends on the mechanical load on the solenoid, its inertia and its frictional loss.
It also depends on how long you need to solenoid to remain its is activated state.
My suggestion would be to try 4700uF and see if it works.

I would also recommend using a monostable such as a 74HC123 and a power transistor. It does add more complexity to your circuit, but it makes the activation time easy to adjust, and it reduces wear on the switch due to sparking caused by the solenoid’s inductance.

Thanks for the information!

After researching your suggestion, I'm thinking my capacitor power idea doesn't meet my 'kiss' requirements.

Would a relay work? Just enough time to throw the solenoid and then permanently latch to coil until the switch is released? That would prevent burning the solenoid. I don't care if that cycle keeps repeating and depletes the battery as long as the duty cycle on the solenoid is maintained.

I'm not sure if the delay in latch time on the relay will power the solenoid. Is there a component I can put at the "?" that would increase the delay time?

Thanks again!

 

I'm curious to know what you intend to trap.
Traps have always been a source of fascination to me.
Good luck........

 

Would a relay work?

It can.
This circuit operates the relay and applies power to the solenoid for appx 1 second when the switch is pressed and held. It will not operate again until the switch is released and C1 has discharged.


This version without Q1 but requires a much larger capacitor depending on relay coil resistance and how much time the solenoid requires.

 

I'm curious to know what you intend to trap.
Traps have always been a source of fascination to me.
Good luck........

Rabbit traps. They ruin my garden every year. Going to thin them out before spring gets here.

I've looked at almost every box trap design on the web and every one has either a complex mechanical jumble of bent wires and trap doors or twine and stick mechanisms that will inevitably jamb at one point or another.

Why no one isn't using a simple low voltage trap door release mechanism & lock is kind of strange? This is the 21st century isn't it?

 

Just run the solenoid power through a maintained toggle switch and position the toggle such that the solenoid strikes it and turns the circuit permanently off once the solenoid reaches full stroke. Then you reset the trap and reset the toggle switch.

Edit: the solenoid itself doesn't necessarily have to be the thing that strikes the toggle. It could be a falling trap door or anything else that moves when the trap springs.

 

It can.
This circuit operates the relay and applies power to the solenoid for appx 1 second when the switch is pressed and held. It will not operate again until the switch is released and C1 has discharged.

View attachment 285543
This version without Q1 but requires a much larger capacitor depending on relay coil resistance and how much time the solenoid requires.
View attachment 285546

Thank you!

I was going through my junk board bin looking for salvage components to test your #2 circuit. I found a magnetic relay door alarm I bought at the dollar store. (The components and the batteries were worth more than a dollar?)

I pulled the reed relay and set this up for a bench test. It worked perfectly. Used a 5v USB battery pack. The reed tripped quickly and there wasn't any erratic fluctuation in the power from reed bounce. At 5v the solenoid is @ .44A. I inspected the reed with a 10x loupe for weld spots and I did not see any. I might invest in a quality reed relay for my final install?

The rabbit would have to jump up and down on the trip plate to ruin the solenoid. Trip plate up or down the circuit is open. It has to be approximately half way to close. I had to cant the magnet to elongate the closed circuit time.

I was trying for simplicity and I think I found it? If you all can see a flaw in this please let me know.

 

Just run the solenoid power through a maintained toggle switch and position the toggle such that the solenoid strikes it and turns the circuit permanently off once the solenoid reaches full stroke. Then you reset the trap and reset the toggle switch.

Edit: the solenoid itself doesn't necessarily have to be the thing that strikes the toggle. It could be a falling trap door or anything else that moves when the trap springs.

That's a great idea!
Have the solenoid perform 2 tasks with 1 action. A door release on the pull side and a toggle throw on the push side. That's creative thinking.

 

I might invest in a quality reed relay for my final install?

From DigiKey, rated at 1 amp. F7907-ND.

 

Thank you for your reply. I trust you are joking about the release part?
Get your own back, eat them!
Fenn trap mark 6?
Have you tried snares, they have worked since man walked upright.
I've found electronics don't work too well outdoors.
I did have some luck with an electronic mouse trap, got the idea from YouTube.
That Australian mouse/rat killer is brilliant, pneumatic.
Good luck.......

 

Thank you for your reply. I trust you are joking about the release part?
Get your own back, eat them!
Fenn trap mark 6?
Have you tried snares, they have worked since man walked upright.
I've found electronics don't work too well outdoors.
I did have some luck with an electronic mouse trap, got the idea from YouTube.
That Australian mouse/rat killer is brilliant, pneumatic.
Good luck.......

Eating a " US suburban grown" rabbit??

If you're looking for a meat source that could likely turn you into a super hero or super villain ,,,,,,,, than it's a good idea. This Millennial "ME ME ME" society is turning this nation into an EPA nightmare with their insatiable appetite for Chinazon e-commerce, palatial homes, and their "throw away" record of filling dumps faster than any generation.

Next to my home is an underground pipe that directs all the drainage water from our sub-division into the woods and then into a creek. After a rain that ditch and creek look like the nuke death scene out of a mad max scifi movie. Oil slicks, Golden brown foam, plastic trash, etc..

I have a front row seat to where those rabbits are forced to survive. Why would I even think of eating them? But I'm sure there is some US Corporation that would love to process them and pass them off as "Organic Grown".