Timpi Electric Solutions
Member
- Location
- Indiana
- Occupation
- Electrician
Greetings,
I've had a job come up in which a customer wants to automate a grain cleaning machine. As it stands, two augers feed grain into the hopper of the grain cleaner. The grain cleaner operates independently of the two augers. Once switched on, the grain cleaner has a "hopper full" switch which is supposed to shut off the auger motors, but it was never hooked up at the time of install. The grain cleaner has no PLC, timing relays, or "hopper empty" switch, as well as the schematic being destroyed by moisture. Currently, the machine operators simply use sight glasses on the hopper and mechanically control the rate at which grain is dropped into the augers with a gate valve to control the rate at which the grain cleaner hopper is filled.
My solution is to add a second sensor switch to the bottom of the grain cleaner's hopper to trigger the auger motors to turn back on, and tie both level switches into the control circuits of the two augers. Simply put, once an auger is switched on, the auger will convey grain into the hopper until the "hopper full" switch closes, at which time the auger will turn off. The grain cleaner will operate, and the the auger motor will switch back on once the "hopper empty" switch either opens or closes.
My question, ultimately, is about the suitability of a standard diffuse photoelectric sensor which I have on the shelf left over from a previous project. It is IP67/NEMA 4 rated, is adjustable, NPN or PNP, and both light and dark sensing. For reference, it is Allen-Bradley Cat. 42CM-D1MPAL-D4. My concern is that the face of the sensor may suffer abrasions over time from the flow of grain, and I'm unsure how significantly this would affect its light sensing capability. I realize that a photoelectric sensor isn't the ideal product to use for this application, but I'd like to get rid of it AND the customer is one of the penny pinching types, but I ultimately want to supply a quality end product. Does anyone have any experience with using photoelectric sensors in applications where the sensor will be immersed in dry granules and subjected to likely a fair amount of vibrations?
I've had a job come up in which a customer wants to automate a grain cleaning machine. As it stands, two augers feed grain into the hopper of the grain cleaner. The grain cleaner operates independently of the two augers. Once switched on, the grain cleaner has a "hopper full" switch which is supposed to shut off the auger motors, but it was never hooked up at the time of install. The grain cleaner has no PLC, timing relays, or "hopper empty" switch, as well as the schematic being destroyed by moisture. Currently, the machine operators simply use sight glasses on the hopper and mechanically control the rate at which grain is dropped into the augers with a gate valve to control the rate at which the grain cleaner hopper is filled.
My solution is to add a second sensor switch to the bottom of the grain cleaner's hopper to trigger the auger motors to turn back on, and tie both level switches into the control circuits of the two augers. Simply put, once an auger is switched on, the auger will convey grain into the hopper until the "hopper full" switch closes, at which time the auger will turn off. The grain cleaner will operate, and the the auger motor will switch back on once the "hopper empty" switch either opens or closes.
My question, ultimately, is about the suitability of a standard diffuse photoelectric sensor which I have on the shelf left over from a previous project. It is IP67/NEMA 4 rated, is adjustable, NPN or PNP, and both light and dark sensing. For reference, it is Allen-Bradley Cat. 42CM-D1MPAL-D4. My concern is that the face of the sensor may suffer abrasions over time from the flow of grain, and I'm unsure how significantly this would affect its light sensing capability. I realize that a photoelectric sensor isn't the ideal product to use for this application, but I'd like to get rid of it AND the customer is one of the penny pinching types, but I ultimately want to supply a quality end product. Does anyone have any experience with using photoelectric sensors in applications where the sensor will be immersed in dry granules and subjected to likely a fair amount of vibrations?
....gasp...
I just finished writing the PLC program, and the PLC and sensor cordset should be delivered sometime today. I will probably just install the sensor that I have on hand and see what happens. Worst case scenario, it doesn't function well and I'm in the same exact position as I am right now, but it at least buys me a little time to source another product.