Simple motor control. - Page 1
Forum section: electronics / beginners

author: moontide
author_rank: Contributor
timestamp: October 02, 2018, 05:33:44 am
content: So I'm a beginner and need a specific problem solved.I work with a conveyor system and have some basic logic control requirements....PLEASE HELP!!!!Problem:Boxes often get jammed on a section of conveyor.The motor does not stop so sinks and shit fall about 20ft onto an area where people may be.Theory:I figure put a photoeye in that area and have it control the motor. If the boxes stay there too long the motor shuts off. (Warning light would be nice too) On startup it should be allowed to run for an adjustable amount of time. (Ideally 5-10 seconds). I can patch into a run signal when the motor would begin.I'm good at soldering and have a head on my shoulders but frankly I'm 1st year industrial tech and the company who installed it can't seem to be able to install a guard requiring no tools. So alone, lol.I watch Dave a lot but I'm only getting pieces.Motor: 3phase 480 acRun signal 120v dcPhoto eye 24 vdc (PNP or npn)Its hard for me to get the inicial run vs normal run.....This problem made me wonder if there is an inductor with 4 contacts... Basically a transformer but an inductor that only passes a voltange threshold....I call it transformative inductor.... Lol.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 02, 2018, 06:00:12 am
content: Quote from: moontide on October 02, 2018, 05:33:44 amyou have few options..1) infrared sensor measuring distance to object from one end of conveyor.2) array of photodiode + infrared sensors on conveyor's side.3) array of weight sensors underside of conveyor.4) motor current spike circuit.5) AI cameranot sure what you can control and how the conveyor looks like.. so..

author: IconicPCB
author_rank: Super Contributor
timestamp: October 02, 2018, 06:53:15 am
content: And yet another option.A timer whihc gets to shut the line down if there are no boxes moving and allowing the light beam to be un interrupted.More simply a timer whihc gets held at zero while beam is not broken.Once the boxes pile up and stop moving beam is continually interrupted , timer times out and stops motor.All done with off the shelf Sick or similar modules.

author: moontide
author_rank: Contributor
timestamp: October 02, 2018, 07:34:28 am
content: I'm all about the timer option but really don't know how to make it work.I find it hard to do a timer when it needs to run initially for 5-10 seconds regardless of photoeye.But thx for quick feedback!

author: moontide
author_rank: Contributor
timestamp: October 02, 2018, 07:52:44 am
content: Its like you have the run signal, but then you have to get rid of it....I'm going circuit level......

author: tpowell1830
author_rank: Frequent Contributor
timestamp: October 02, 2018, 09:44:07 am
content: Probably a good place to start is to chart out your process flow. This simple chart is very helpful in order to get your logical flow down first and then decide how this sequence will work electrically.EDIT: I used this method numerous times when designing logic for PLCs in an industrial environment. Just use a pen and paper and draw it out by hand.

author: rstofer
author_rank: Super Contributor
timestamp: October 02, 2018, 05:38:13 pm
content: It seems to me you have a fairly dangerous system where parts are moving high over the workers below. Second, you aren't really up on industrial controls (PLCs and such). I think you should leave this to the engineers, manufacturers or contractors. The fact that product can fall from the conveyor is sufficient reason to limit your personal liability.Without seeing the installation, physical and electrical, it's hard to say which method to use. Jam detection has been done on conveyors since the day after the first conveyor was installed. At floor level this isn't such a big deal. At elevation there is a real problem.

author: Old Printer
author_rank: Frequent Contributor
timestamp: October 02, 2018, 07:13:41 pm
content: Does OSHA ring a bell?

author: rstofer
author_rank: Super Contributor
timestamp: October 02, 2018, 07:25:57 pm
content: Quote from: Old Printer on October 02, 2018, 07:13:41 pmWhy yes, yes it does! In my case CalOSHA - the homegrown variant.There is a chain of responsibility here from the company, through the contractor, then the engineer and on to the manufacturer. There is no good reason to go to the head of the list. The last guy to touch it, owns it!I worked on this kind of stuff, off and on, for about 40 years. If I couldn't guarantee a 100% solution, I would walk away.This project has no upside and monumental downside, from a personal point of view. I wouldn't want to be "that guy...".

author: moontide
author_rank: Contributor
timestamp: October 02, 2018, 10:38:59 pm
content: I would leave it up to the contractors, engineers and such but they were already here. They put in a photo eye and worked to get the line to prevent jams. After a few attempts they simply gave up and ripped out all the equipment. We made numerous attempts over the past year for them to fix it but they haven't even looked at it again. Our line has 50+ major issues and we spent millions for the install. I'm a first year tech and I've been fixing things that 3+ of their techs could not.So basically its up to me or it won't get fixed.I could wash my hands of it but when someone gets hurt I'm not really going to be worthy of this position.As for the system, there are surely better plc things I could do but access to this will not be given by my company. Rightfully so as I could make things much worse. I think designing a little module would be the most practical or finding a similar solution on the market is good too.To be honest it might take me a few years more to do this. I have such a mental block with this kind of work.... I miss PHP!!!!!! I've learned a bunch of random facts from Dave and so far I've only blown 1 power supplyBTW. We pass OSHA inspections every time.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: October 03, 2018, 12:51:45 am
content: Quote from: moontide on October 02, 2018, 10:38:59 pmI forgot to welcome you to the forum, so Welcome!So what I see in your sequence diagram is that you need to stop the conveyor, and also you said that you do not have access to the PLCs. This is a problem because you need to access the controls for the conveyor, which, I assume is the PLC. How will you resolve this?

author: moontide
author_rank: Contributor
timestamp: October 03, 2018, 02:01:53 am
content: I think I have a solution. It is PLC based but no need. I have wires!!!!!!!!Basically run a couple relays in parallel encompassing the conditions I need. If either are on a closed state it energizes a 480 relay for the motor.Many of the diodes are to protect the collapsing coil energy from returning to the plc since that's where the run signal comes from. The rest are for fun.The photo eye is the signal for the Retriggerable One Shot Relay.I guess no 555 for me:(Lol I got a diode backwards.. but you should get it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 03, 2018, 03:46:38 am
content: Quote from: moontide on October 02, 2018, 10:38:59 pmbased on your conveyor diagram, i suspect the boxes got stuck at the corner? have you look at mechanical solution on to avoid the jam. maybe put additional roller or guard to steer box in correct path? while at airport waiting for my luggage i sometime observe how the conveyor works.

author: moontide
author_rank: Contributor
timestamp: October 03, 2018, 05:03:37 am
content: We worked with mechanical solution and dropped jams down by orders of magnitude but there are many factors. Later I can post a pic of the line before this.3 story belt system2 incline 180*People who place boxes on in a wreckless fashion.Lack of gaps sometimes.Distorted boxes.And only 4 techs with 2 miles of conveyor. 3 are near retirement....I am exploring all options though.As for the welcome.... Happy to finally be here. I mainly have one other project I'd love to do but it is seriously difficult.I actually met Dave in an Arizona bar once. I was kinda a prick. Funny that now I want his help.... And something unrelated to what we talked about.FPGAsReal time video decodingPixel by pixel anilizationTrack predictionSilinoid firing=GOLD... Yarrrr!

author: CCitizenTO
author_rank: Contributor
timestamp: October 04, 2018, 10:23:52 pm
content: Sounds like you need a combination of means to solve the problem.Quote from: Mechatrommer on October 02, 2018, 06:00:12 amTry a method where you have sensors that detect distance to the object on the Y and Z axis assuming X is where the objects flow along the conveyor belt system. Assuming boxes change in shape and size very frequently having two points of data stay the same for a long period of time would indicate a jam.The other aspect is if you have foot traffic below the conveyor belts you should probably cordon off potential drop zones from frequent foot traffic and provide safety barriers to hazardous drops from above to minimize dangers that could cause injury or death to employees. I'm guessing there may be forklifts and the like operating in the facility and those likely have safety ratings on their equipment for falls from above for the occupant of the vehicle but those don't help the employees who aren't certified to operate a forklift.

author: moontide
author_rank: Contributor
timestamp: November 26, 2018, 01:09:22 am
content: Well, thanks a bunch your your input. I'll keep options in mind but we put a bandaid on via relocating existing master photo eyes. Perhaps when I'm better I'll come back for more info on this.My next post... Capacitors, oh capacitors. I'll post soon.