How to build circuit for lifting mechanism

Thread Starter

kksmith

Joined May 23, 2009
5
Hi,
I need to build a simple machine which can work on DC battery but I have no knowledge of electronics may be someone can help me.

Task: I need to move a small platform up & down for hobby project. If I press switch upward it should go up and if I press switch downward then platform should move downward.

Problem:
I can build up mechanical setup but I don't understand how to control motor turn clockwise and anti-clockwise with a switch. Second problem is once it reaches to the extreme limit how to stop motor automatically.

Any help or pointer to right direction would be highly appreciated.

Thanks in advance.
Kevin
 

Bernard

Joined Aug 7, 2008
5,784
What is distance from floor to platform, retracted? Now extended? What is size of platform? What load must it lift?
One option is a scissor jack, using a gear-speed reduced electric motor, threaded shaft, nut two limit switches, & a DPDT relay; also the up-dn switch.
 

jpanhalt

Joined Jan 18, 2008
11,087
The simplest, non-electronic method would use a reversing switch and two limit switches.

The reversing switch can be made from a DPDT switch. I would suggest one with center off. I can't draw you a schematic right now, because that computer has a problem. The two power leads go to the two center terminals. The motor leads go to one set of the outer terminals, and two wires crisscross to the other set of outer terminals. Just look up how to wire a reversing switch. An alternative to a toggle switch is a push-button switch. Commercial versions can be quite expensive, if bought retail. You want a lock-out switch, so you can't push up and down at the same time.

Limit switches are self-explanatory. They simply switch off the power when the lift moves the actuating lever.

John
 

Thread Starter

kksmith

Joined May 23, 2009
5
Thanks for quick replies, it's not very heavy to lift.
Scissor type jack system can work well.
It needs to move about 80mm and weight is approx 300 grams.

I looked at computer cd mechanism which is perfect example what I need. I can pull out cd tray from old computer but I need to run on batteries so that I can easily take to different places without worrying about power supply.

Thanks
Kevin
 

lightingman

Joined Apr 19, 2007
374
Hi.

I have just built a system that does just what you require. It was for an award ceremony and it had to lift trophies up and down.
I used a PIC16F877 Microcontroller running at 4Mhz. The motor was PWM controlled so that the speed up and down could be set and limit switches did the business of stopping in both directions. It had an up, down and stop switch and would automatically move to the up possition on start-up.

If this would help you, I could let you have all the details and PCB layouts, and could progam you an 877 if you can not do it yourself.

Where are you?

I am away for a week on holiday, so I can not do anything and have no internet connection until I get back next Saturday.

Daniel.
 

Thread Starter

kksmith

Joined May 23, 2009
5
Hi Daniel,
It seems to be you're the right person with all the details what I need.
It would be really great if you can arrange circuit layout for me. There is no rush you can take your time. I'm based in Australia.
Cheers,
Kevin
 

SgtWookie

Joined Jul 17, 2007
22,230
If you just want something really simple that consists of just a DC motor, a DPDT (Double Pole Double Throw) toggle switch and a couple of NC (Normally Closed) limit switches, you could use this:



S1 is the DPDT switch.
S2 and S3 are the limit switches.

There is no braking provided with this circuit, so the motor will take a moment or two to stop.
 

Attachments

Thread Starter

kksmith

Joined May 23, 2009
5
I'm bit stuck at mechanical lifting mechanism at this stage. I built up simple scissor type lifting system and used toy motor. It works fine but I'm not very satisfied with the results because of excessive friction.

Now I'm inclined towards CD tray ejection system which I can directly connect to my lifting object.

My question is: Can I run cd ejector assy with battery?

Thanks
Kevin
 

Thread Starter

kksmith

Joined May 23, 2009
5
does it need to be self holding at any position?
can the platform travel along a vertical support, or must everything be below the platform?
It doesn't need to stop in-between. If it stops on topmost and lowest point I'm happy with that.

I'm thinking to use kitchen drawer slides to support and move unit up & down. It doesn't matter if lifting mechanism protrudes above the platform.
Kevin
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
I'm thinking to use kitchen drawer slides to support and move unit up & down.
Kind of overkill for 80mm.

That old bubble jet printer your ready to throw out, or some else's. Rip that puppy apart and extract the tub traversing mechanism. You'll find a great linear drive system that with a bit of modification will accept your platform. The drive motor will be stepper, but if you want you can replace it with a gearmotor, as you will certainly need some speed reduction/torque multiplier. Should even have limit switches.

Depending on you skills, you may want to keep the stepper, maybe even some or all of the controller to hack away.
 
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