master line speed with multiple conveyors

I have a application where I need to control multiple conveyors with master line speed control in a HMI and PLC. Currently I use 12v power supply and scale it to 10v with 500ohm pot. I have 1k pot for master line speed and 100k trim pots for each conveyor drive. This lets me pull a gap between each conveyor and use the master to increase or decrease line speed. Does anyone have a program I can review or how I may go about this? I'm using controllogixs and PV+

So, you are replacing pots with PLC and analog outputs?

If that's the case, then you should be able to calculate everything in engineering units, including the trim values.

I would have a scale factor for each drive that will turn the master reference units into drive speed command units. This will allow gear changes on individual lines to be easily dealt with.

For the trim values, you may just want to use a percentage. For example, the first conveyor trim factor might be 1.00, the next conveyor might be 1.05, and so on.

You could also apply multiple scale factors to each successive conveyors, so that, for example, conveyor two runs at 1.05 times the master, and conveyor three runs at 1.03 times the speed of conveyor 2. Doing that would ensure that each successive conveyor always changes with any adjustment to upstream conveyors.

The above is just an idea about how to program this, but perhaps you are needing info about the hardware to choose?

Paul

I was getting ready to make a suggestion and then read Paul's post. I agree with him, just subtract you individual trim value from your master value. We do it a little different here, our speeds have to maintain the same 'ratio' so we multiply the trim values by the master value.

As far as equipment we use Red Lion G3 touchscreen HMI's and Omron CJ1m plcs (on the drives that don't have modbus). If your drives are modbus capable you may not even need the PLC

Michael

Paul's dead on, and what a great way he explained it.

Choose a master and then let the operator set ratios for each of the followers.

I did the same the other day a little bit different, but here it goes:
Use a master reference pot from 0-10 VDC source this is an input to ana analog board. As an example 0 means 0 rpm 10 VDC means 1750 rpm
Use several pots even from the same dc power supply but this time I use a scale, example -25-0-25 rpm, 0 means -25 rpm, 5 volts means no change, 10 volts means +25 rpm, this way your slaves can run slower or faster than master.
You can change scale as needed.

Simpler still!
One analogue output to master drive analogue input.
Use analogue output of first drive to analogue input of first slave.
Do the same for first slave analogue output to second slave analogue input.
etc. etc.
Scale the analogue input of each drive accordingly.
By adjusting the speed of the master drive all slaves will follow.

This only works if you do NOT wish to change the relative speed [gap]of each slave to master from the PLC/HMI. In this case you will have to manually modify the analogue speed reference parameter in each drive.

If you DO want to change relative speeds then throw out the analogue idea and put all drives on a network [Modbus, Devicenet etc.] then you will have full access and control to all drive parameters.

We use BnB basic idea with the addition of a swcond analog in for a trim to each drive. This allows us to very the differnce between each individual drive. A lot of drives will allow some type trim input. If your drives don't use the other ideas posted here and do it all in the PLC.