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Hello all,

 

For my final theoretical project for my college course, I am required to build something which requires a PLC or a microcontroller.

 

I have decided to build a portable PLC controlled rotiserrie machine.

 

I haven't determined all the parts that I need for this project yet, but was wondering if someone can help me out figure out if its possible

 

I belive that the Unitronics M91 PLC wll be suitable for this project. I will have a portable 12VDC supply (Car Booster Pack) to power the PLC.

 

I require the PLC to:

 

- Set/ Operate a (stepper or geard) motor to spin the spit in a clockwise and counterclock wise direction.

- Set/ Operate a (stepper or geard) motor to raise and lower the spit.

- Measure and display 2 anolog temperature sensor readings

- Measure and display the speed from a tachogenerator

- Contain programable "set time" operations

- Contain display with time of day and other varibles.

 

Can this be done? What limitations will I encounter?

I would really appreicate some help

 

Thank you

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Hi,

 

I would suggest using 24VDC.  Either use a voltage booster (you can get these from automotive accessory suppliers and electronics stores), or use two smaller lead-acid batteries wired in series, like alarm or UPS batteries.

 

If you really need to use 12V, there are only certain models of M91 you can use.  You will then need to make some compromises about the types of signals you can use and how you will interface with the motors and sensors.

 

With 24V you can use the Jazz series.

 

For example if you use the JZ10-11-PT15, my comments are below starting with ##

 

- Set/ Operate a (stepper or geard) motor to spin the spit in a clockwise and counterclock wise direction.

## you can use the HSO (High speed output) on the Jazz to control the stepper (through a controller/amplifier) and have direct speed control.  Use a normal digital ouput for Fwd/Rev selection.  Just check pulse rates and gearing to make sure you can get the RPM you need from the combination of Jazz and stepper.

- Set/ Operate a (stepper or geard) motor to raise and lower the spit.

## use a digital output for simple on/off control, use a fixed speed geared DC motor.

- Measure and display 2 anolog temperature sensor readings

## purchase PT1000 probes that can connect directly to the Jazz unit without needing an interface module.

- Measure and display the speed from a tachogenerator

## use 0...10V analogue input to read this signal (depending on the tacho used),.  This PLC also has a pulse input, for pulse style tacho signals.  The LCD display can show the value.  Note that if you use a stepper, and have no pole slipping, then the rotational speed is determined by the speed of pulses to the stepper and external feedback is not required.

- Contain programable "set time" operations

## easy in M91 or Jazz

- Contain display with time of day and other varibles.

## generally easy in M91 or Jazz.

 

 

You can run into other unforeseen limitations with the Jazz, so another option is the V130.  For example the V130-33-TRA22 has just about everything you would need built-in, with more flexibility than the Jazz.

 

I hope this helps.

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I accidentally bought a 12v power supply for development work with a v570 and used it for months before I discovered my mistake. I certainly wouldn't want to install a 12v power supply on a project at a customer installation, but I never had a hiccup. Yes, I didn't have any I/O modules attached and that might make a difference, but the Unitronics PLCs are very forgiving when it comes to voltage.

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The V570 T20B units are specified for 12/24V for just the PLC/HMI without I/O.  The older style T40B with cold-cathode backlight is only 24V.

In general, any of the PLCs without I/O can run on 12 or 24V, including the V130-33-B1 and V350-35-B1 (and their "J" equivalents).

 

It's the I/O modules that are more particular about supply voltage.  For example, with digital inputs the switching thresholds are based on 24V, so 12V applied to a 24V input will not be enough to switch it on.  The threshold is usually around 17V (this is specified in the datasheets for each module).  There are issues with digital outputs as well, but I won't blabber on and on.

 

Also, in the M91/V120 families, none of the models with analogue outputs have a 12V option, they are 24V only.

When looking at the "-L" I/O modules, there is also an absence of analogue output models.

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