Adjustable Solenoid Needed

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PrIsMaTiC
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Joined: Mon Nov 07, 2005 1:01 am
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Adjustable Solenoid Needed

Post by PrIsMaTiC » Thu Feb 01, 2007 2:12 pm

I want to control the movement of a small aluminum lever
attached to a spring. I'm using a simple machine screw
to adjust the position of the lever, but I'd like to build
a control circuit that would sense a voltage change and
energize a solenoid. Building the control circuit is no
problem for me, but I need help in selecting a solenoid.

I haven't measured the force required to operate the lever.
The solenoid would have to be more of a push type than
pull, since the lever is under tension when it is depressed.
I'm guessing it requires three to four pounds of force. If
I can find a source that might be able to supply the solenoid
I need, I'll use a gauge to measure the force required
to operate the lever.

The solenoid must be 12 vdc or less. 1/4 inch plunger
travel should be more than enough. Here's the problem.
The distance from the plunger to the lever may have to
be adjusted several times. If I have to use shims or
different size brackets I might as well keep adjusting
the lever with a machine screw. Is there a solenoid
where the plunger travel can be adjusted easily?
Maybe some kind of screw adjuster in the body of the
solenoid.

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Dave Dixon
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Location: Wichita, KS
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Post by Dave Dixon » Fri Feb 02, 2007 5:43 am

One of our engineers bought a fish scale from a disount store for a similar project. You should have seen the look on the face of him, and our metrologist, when I told them it needed to be certified. It had a big colorful picture of a bass on it!!! Hated to cover it up with a calibration sticker ! ! I'm sure this doesn't help you, but it IS Friday :)
Dave

PrIsMaTiC
Posts: 48
Joined: Mon Nov 07, 2005 1:01 am
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Post by PrIsMaTiC » Fri Feb 02, 2007 7:17 am

Hello Dave.

This thing I built is mounted under my dad's car. I don't
know how many people in the USA drive a car with a manual
transaxle/transmission, but he's one of them.

He developed a serious problem with his right shoulder,
which causes him pain when he shifts gears. The device
I built allows him to shift with less stress on his shoulder.

What I didn't realize is the darn thing needs small adjustments
to keep it working. I don't want to put the car up on ramps
every couple of weeks, like I'm doing now.

Using a fish scale to measure force or torque is only a bad idea
if precision is required. I don't know how many times I've used
improvised methods of obtaining a measurement.

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Chris Smith
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Location: Bieber Ca.

Post by Chris Smith » Fri Feb 02, 2007 7:52 am

For a strong relay action the stepper motor or clacker gear type of solenoid will do the trick.

A small motor or solenoid can ratchet a screw thread [and catcher gear] forward until the lever is pulled or pushed, a little bit slower but stronger than electro mechanical actuators per se.

The two types can involve either a ratcheting solenoid that clicks fast and forward to ratchet a shaft that pulls with a great force, or the second type uses a stepper motor and square thread and shaft to advance the movement, both using very little actuating force and long distances as well as a great force on the movement it self.

Delay is the only draw back as most actuators may take a second or more to fully engage.

Both act like a car jack in that they both move a little slower, but actuate a greater force over all.

A ounce of force may move tens of pounds with the right ratio of leverage.

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