I'm trying to figure out an easy way to have the machine (rather than the operator) record downtime for more accurate efficiency calculations.
The cheapest way I can think of is to add an hour meter to the primary circuit so that it can simply be read as required.
I have heard of high-end recording systems that run to $5K per machine, and probably have all kinds of reporting features, but I'd like the explore the cheaper end of the spectrum before I resort to something that expensive.
My biggest requirement is that the method not be easily defeated. I want the report to be _accurate_.

If you have a signal that can be read, which equates to uptime (or for that matter downtime) feed this into a cheap PLC timer and count it there.

For example, I used to work on a robotic assembly lines with up to thirteen robots all doing different parts of the assembly process. For process control reasons we had to measure the amount of time that the robots were idle. There was a warning light on the robot that came on when it was moving. We just took the signal from this and input it to a PLC to count the time that it was working.

quote:

Originally posted by Bryan Weir:
If you have a signal that can be read, which equates to uptime (or for that matter downtime) feed this into a cheap PLC timer and count it there.

The biggest stumbling block that I see is that these machines are plastic extruders with large DC drives. These are functionally similar to a standard variable frequency motor drive in that they are adjustable from zero to full speed. I want to be able to record the time that the motor is actually 'working' but I don't want it to include idling time. In other words, the easy way to trigger it is to use the power signal, but just because the motor drive is 'on' doesn't mean the motor is turning or doing any work. I suppose I need to find a way to read the amperage and have the timer triggered only when the amperage is above some set level, like 20A or something.
I've seen special motor hour meters that actually detect the electrical field in the motor, and only 'count' when the motor is running. I might look into these, and there is also the possibility of using an hour meter that is based on vibration. These are all cheap and easy (<=$100 per machine) solutions, but there might be better solutions out there.

There must be a signal somewhere that tells the motor to change from idling to working. If you can find and use that you have cracked it.