So, to start off, here is my problem. I have to measure conveyor belt speed at work. It is a very tedious process because the fastest belt speed is 12 IPM, the slower being around 2 IPM. It is very difficult to get consistent readings with a stop watch and measure something moving that slow. Especially without being interrupted by someone or something.

I then have to take the numbers I come up with and adjust the VFD on the conveyor drive motor to get the belt moving at the proper speed called for on the product that is in the oven.

My idea was to design and build a timer, with a laser photodiode that triggers a start timer, the product travels 12 inches, then, triggers a second laser photodiode that stops the timer. Then I can convert the seconds/foot to IPM.

I have seen pinewood derby arduino timers that look like they would fit the bill. But, most of those call for a pc to carry around to track lap times. That a quite a bit more than I need at this moment. I am looking for something more simple.

I used the search function here and google, and couldn’t find anything exactly what I’m looking for. Is there any documented project on here, or that is known about elsewhere that may fit my needs?

 

One way would be to use a proximity detector on the conveyor/belt and input into a SmartRelay, these have several timers etc, It sounds like you intend changing the VFD speed manually?
If using the SmartRelay, you could set up the VFD for multi-speed input, most have up to 16 preset speed capabilities to cover the rpm range you may need.
This would then be an auto or semi-auto system.
Or do the same with a small Picmicro.
Max.

 

It sounds like you have quite a bit of experience in PLC’s. That sounds like a really good idea and part of my end goal is to have presets for different products in the oven. We have been relying on the machine operators “feel” for the belt speed. Basically, if they want to go to break sooner, or get their production numbers up, they increase the belt speed to save time.

I pretty much just need to measure the belt speed on 10 different ovens to come up a list of VFD settings to stop the, playing it by ear. So, the speed measurement device is preferred to be portable, cheap-ish and essentially disposable. As we will be switching to a different procedure in the near future.

So, essentially, what I want is a magnetically mounting, portable stop watch, that is triggered by opening the circuit of a photo optical switch to start a stop watch. Then, opening the second circuit, 12” away to stop the timer.

 

If you don't want to incur much cost at first, you may be able to adapt a simple $5.00 timer, ebay 322568088183.
The timer could be adapted for a sensor input etc.
Max.

 

If the drive roller or idlers are available to apply reflective markers, then a portable photo reflective sensor
driving a counter could be used?