Hi, I am trying to devise a circuit to control a conveyor belt. What needs to happen is that three items stack on the conveyor, the conveyor moves for 1 second and stops, and this sequence repeats.
I thought of 1/3 threshold voltage applied to a capacitor feeding a compariator/op-amp that feeds a control replay to start the conveyor. Bleed off of cap would stop.
Any help???

 

What you want is called a jog position on a AC or DC speed control. This allows a momentary run command to be utilized to un-jam a belt or a load.
A free running (astable) multivibrator w/ inhibit line can be paralled with the jog switch on the drive to achieve this function.

Cheers, DPW [ Everything has limitations...and I hate limitations.]

 

A 555 Timer is a more simple approach I believe

 

Possibly a 4017 as a counter, then feed the third output to a monostable timer than runs the conveyor and resets the counter.

 

If it a continuing sequence we need an off time, or a better definition of project.

 

Hi, I am trying to devise a circuit to control a conveyor belt. What needs to happen is that three items stack on the conveyor, the conveyor moves for 1 second and stops, and this sequence repeats.

Moves for 1 second at what speed? Wouldn't it be more important to have a "location" to pinpoint rather than relying on timing?? If the 1 second time delay was even off for 100th of a sec, every 100 seconds the conveyor will be off in position. If the belt had a "start" and "stop" indicator then it would be easy to always line up the item on the belt with whatever you are lining it up with..... As in grocery stores checkout's, there is an IR sensor and emitter that tells the belt when to stop once the items reach the cashier... once the item is removed, it will move the belt again until IR beam is again broken...... if the belt runs for so many secs (time delayed), and no items ever reach the sensor, the belt turns off...


B. Morse

 

The product is question is hand packed into a three pack pouch. Production rate is ~35 pieces/minute, continuous conveyor transports from machine exit to packing area. Packers scoop three (one at a time) and place in a pouch.
What I am trying to do is prox switch or micro switch product exit-(clock pulse one, two, three...move conveyor for a product width..stop.. wait for clock pulse one, two, three, move again one product width....repeat.
The packers would then grab three pieces, insert into pouch..repeat.

I dummied up a circuit using a 4017 output 0,1,2 to a 4073 three input AND gate but looking at the output tree from the 4017 it seems that at the second clock pulse output 0 goes back to 0...thus no dice

 

The product is question is hand packed into a three pack pouch. Production rate is ~35 pieces/minute, continuous conveyor transports from machine exit to packing area. Packers scoop three (one at a time) and place in a pouch.
What I am trying to do is prox switch or micro switch product exit-(clock pulse one, two, three...move conveyor for a product width..stop.. wait for clock pulse one, two, three, move again one product width....repeat.
The packers would then grab three pieces, insert into pouch..repeat.

I dummied up a circuit using a 4017 output 0,1,2 to a 4073 three input AND gate but looking at the output tree from the 4017 it seems that at the second clock pulse output 0 goes back to 0...thus no dice

So does the conveyor have to reverse to reset the product being picked?
So the picker starts from product one, conveyor moves so picker can access product 2, up to the third product then the conveyor reverses so the picker can start from product one again?

I guess I am a little confused on what you are trying to accomplish here.... Maybe if you elaborate a little more, your descriptions of the process are a bit vague...

B. Morse

 

The product lands on the conveyor from a suction cupped wrap spring. The conveyor is moving continuously.
The packers need three pieces of product to fill a pouch (sorry about decscriptions...I need anominity for the business).
What I am trying to do is to have the production machine make three pieces of product stacking one on top of another until a stack of three is made then jog the conveyor a width of the product then stop. Repeat.
This way the packers are taking a complete stack of three bags and sliding them into a pouch. They have to pick up three pieces individually now and it is hard to pick up the third while holding onto two. If I can make the conveyor do what I want, they can just grab the stack of three and pack.
Does that help?

 

I think I get what you are trying to do, so basically you want to count to 3 then move conveyor a preset distance so another 3 products can stack on top of each other, then the belt moves again..... ok so no reversing required just a constant flow........

Lets start with a few things here that are kind of important.....

1. What kind of motor is it, AC or DC?
2. What are the ratings for said motor?
3. Is there any type of motor contactor or motor control circuit already in place?

So once we have the motor specs, then we could recommend a circuit or relay capable of handling that load.

If it is an AC Motor (1 Phase, etc.), I would recommend looking into getting a Motor Starter Contactor similar to the pic below:

Make sure it is capable of handling the motor.... also don't forget to get a surge suppressor for the contactor when you get it (small electronic device in pic above), this will alleviate issues with back EMF when you turn off the coil.....

You can then use a solid state relay to activate the motor contactor from a TTL level logic signal, (from counter, timer circuit, etc)....

And since this is a "factory" setting, you will need to use UL listed devices for starting, and stopping the conveyor, look for some retroreflective photosensors to use as your sensors, these will usually come with a reflector.....similar to pic below...


B. Morse

 

You need one of these..... http://en.wikipedia.org/wiki/Geneva_drive

 

Is the product such that it can be counted by broken light beam as it drops to conveyor, then on count 3, starts conveyor till B Morse's ,pg 6, beam stops conveyor? A magnetic particle clutch might be used between motor & belt drive to allow continuous motor run.

 

Yes, I could easily use a interupter or reflective sensor to toggle pulses, even a dragging microswitch arm.
The motor is driven by a VFDrive for speed control and it has a jog button that I could parallel for intermittant service.

 

Does jog sw advance or stop belt? What voltage or grounds are on jog sw contacts, AC, DC , low or high voltage??

 

Jog switch advances belt until centered.
Swicth is three position- JOG-OFF-RUN
It is DC

 

Here is a straw man to throw knives at: Assuming a positive pulse for each falling product as input to 4017 counter, on third drop , pin 3 goes high untill reset giving a verry narrow + pulse to trigger 555, output set by 100k pot gives a 1 to 1.7 sec + pulse, & with proper conditioning triggers jog sw to advance belt.

 

Rotate print

 

Would the third clock pulse set pin 3 of the 555 High?
That is the first cycle I can pick off to drive the conveyor with a contactor, relay or whatever, that part I can do easy. Now I need to reset the 4017 to repeat the cycle.
I can do it once with what I know from the drawing..but then the conveyor has to move whilst the product is getting to alight on the future stopped conveyor.
The conveyor movement needs to occur while the product carrying arm is approaching but not yet arrived. As the conveyor is moving the product placement arm is getting ready to sequence pulse 1.
How fast is the 4017 reset time?

 

By the way Bernard, I appreciate the hell out of your helping me with this.
It is a "can you do it?" project at work and a chance for me to keep my mind going with my electronics.

 

And this 83 yr OL guy does it for the same reason- hold off big "A" for a few more years.
Some new players, " product carring arm, & placememt arm "; not sure how they fit the equasion.
4017 is reset ~ 20 n sec after 3dr stage goes high, followed by a few n sec. later, 555-pin 3 goes high for timing period. Belt should start moveing just as soon as 3rd product drops.
If we knew what was on the jog sw contacts, might better define interface between 555 & jog sw. or can use electro-magnetic or solid state DC relay.