scroll wheel components and other uses for them

[kinarfi]

May I refer you to someone else's photo?
https://www.electro-tech-online.com...logitech-mouse-scroll-wheel.87241/#post680265
I believe the item on the right is a IR diode.
I'm not sure what the receiver is or how it works, but while playing with one, trying to make a position sensor out of one, I discovered that it may be photo voltaic. Does any one know for sure how this item works?
My real need is to make a sensor to detect when a shaft has receded to a point so I can energize a coil for .030 seconds to raise it back up and start the process over. This is on a fuel pump that keeps burning up the contacts and a new pump is $140
I would appreciate any help I can get on learning what that device on the left of the photo is and maybe some suggestions on a good sensor for when the shaft is down. I thought about a hall effect device, but when the coil energizes, there's too much flux flowing for a hall effect device. I had some strain gauge devices, but I can't find them, so I think optical would be optimal
Thanks,
Kinarfi

 

[Joe G]

this will give you a good start.

also look at Photo-interupter switches, there are some made to go over a tube to detect fluids that may work for you shaft.

 

[Mr RB]

With either the hall effect device OR the IR sensor, you will still need something like a FET or transistor to switch the coil current.

My vote would be for the hall sensor, it is immune to dirt etc and can be a type that has a digital output (making it easier to drive a FET, as it is always exactly ON or OFF).

 

[kinarfi]

I tried the hall effect device and magnet's flux was swamped by the flux from the coil, what I have right now is a photo cell on one side of the shaft and a LED on the other that has a piece of shrink tubing on it to restrict the light to a small beam that the shaft breaks when it is driven upward, the resistance of the photo cell changes from KΩs to 100s of KΩs, I'll use that as the trigger for a 555 one shot timer and the 555 out will drive an N FET

add on - The fuel pump has a sealed cap over the end with a vent tube, the points would create some dust, but the chamber should stay clean with out the points.

 

[kinarfi]

Rather than start a new thread about the same item
I have a solenoid type fuel pump that operated on a set of contacts that toggled like a microswitch's contacts as the plunger went up and down switching an inductive load of ≈ 5 amp at an estimated frequency of 1 to 2 hz which pitted the contacts and failed the pump. I rebuilt the pump using a photo cell and an LED and it works very well IMHO.
I'm trying to tune the pulse time for the solenoid so it has enough time to completely pull in, yet not give any extra time which would only serve to heat the solenoid.
I have attached a "photo chopped" scope shot that I have added notes to and would appreciate it some one can confirm what I think is happening. I used a .1Ω resistor in the line to the solenoid to monitor the current with my scope.
Thanks,
Kinarfi

 

[alec_t]

I think your supposition that the current reduction indicates solenoid movement is correct. The movement of the armature generates a back-emf to counter the applied 13V. A similar effect occurs in fuel-injectors.

 

[kinarfi]

Thanks for your come back alec_t!
Kinarfi