Actulator/Solenoid Help

[Marsh Lane]

Hello all,
Im new to the forum, so hopefully posting in the right place. Im just getting into electronics, but am a bit new to things!

Currently, I'm working on a little home project involving a lever that is connected to some 2mm brass bar. As the lever moves forwards and backwards, the brass bar moves as well. Now at some points I need to lock the lever, so my idea is a small wedge cut out in the forward and backward positions (shown as F and B on the attached drawing), now that bit I'm fine with, but my thought was to move the 'U' shape that pushes or pulls the 'wedges' into position using an Actulator or Solenoid to create linear movement.

I can control the power to the device using an electronic circuit no problem. But the issue is that Actulators seem to be running in the £70-£90 each mark (I'm in the UK), and Im likely to need 10-20 of them, making it very expensive! My other idea was a solenoid, but given that it may remain powered for some time (i.e. upwards of 40-50 minutes) I suspect the solenoids will burn out quickly.

Before I start looking to use stepper motors and create my own form of actuator design (with the inherent problems) can anyone suggest an alternative way of motorising the movement of the 'U' shape? For reference, there may be times when the 'wedges' do not line up immediately, and one wedge is being pushed against the full width of the bar, only dropping into the wedge hole when the lever is moved, hence there does need to be a constant, but not excessive, force until the 'U' has travelled its full distance. Only one of the two wedges will ever be required at any one time.

More than happy to adapt the design to another way of stopping the brass bar (and hence the lever) from moving if anyone has any thoughts.

Activation (or deactivation) of the whole device will be undertaken using relays and logic gates.

Cheers
Richard

 

[Bluejets]

RC servos perhaps.
Add a spring to the output arm for the period when the latch is not yet engaged.

 

[Marsh Lane]

Hi Bluejets,
Hmm, hadn't thought of that - they could be controlled from a PIC processor with a PMW output I suppose. Will a servo try and keep pushing until it reaches the set limit? I presume that wouldn't burn it out?

Rich

 

[duke37]

You seem to want very little movement, could you adapt relay?
Post office relays turn up at radio rallies for not much dinero.

Film projectors used a device for traversing the film (Geneva drive?), this could be switched off once in the locked position.

 

[Marsh Lane]

Hi Duke37,
Interesting idea - Im relatively new to electronics, but I always thought a relay was an internal electric switch - is there some form of movement on Post Office relays? Are they relatively easy to adapt?

Rich

 

[duke37]

Relays consist of a solenoid which pulls a pole piece a short distance to activate electrial contacts. They are made to be efficient and to stand contiuous use. You will need mechanical skills to adapt them.
An ordinary solenoid is probably designed for a large travel distance so the magnetic circuit is not optimum.
I suggest you go to a car breakers and get some automobile relays and use your big hammer to investigate them.

 

[Marsh Lane]

Thanks for that, i'l take a look!

Rich

 

[Bluejets]

Hi Bluejets,
Hmm, hadn't thought of that - they could be controlled from a PIC processor with a PMW output I suppose. Will a servo try and keep pushing until it reaches the set limit? I presume that wouldn't burn it out?

Rich

Idea of the spring is to allow servo to travel to the set position. If not, the feedback internal pot will be telling the motor to "soldier on" and it will be sitting there buzzing it's head off trying to get to the set point. Also allows for a bit of leeway in the setting of the servo position( does not have to be spot on). $2.00 servo controllers off Ebay can drive the servos, as would a picaxe or an already built Arduino mini with a pre-written bit of servo code. Heaps out there.