- Tue Nov 12, 2013 9:51 am
#165483
Background: I have a special printer that is used for printing on various items... dog tags, pens, baseballs, etc. The printer has an auto adjusting bed - you place an item on the bed, hit auto height, the bed raises to the max height, then starts advancing into the printer. If anything trips the height sensor, the bed stops, and starts moving down until the sensor clears, then it advances forward again. Eventually everything clears the sensor and you're good to print.
Well mine was both not calibrated correctly upon receiving it, and as well, depending on the item you place on the bed - sometimes it would not read right. I had the print head hit a bottelcap I was printing on as the auto sensor did not work correctly.
I open the printer up and see the emitter is a BY500-TDT1 and the sensor is a BY500-TDT2. Looks like a simple infrared emitter/detector. Now, I dont have a camera capable of IR detection handy, but I'd venture to guess that the scatter of the infrared beam would not be overly accurate. Real great for sensing when the beam is broken, but real poor at sensing within 10ths of a mm when the beam is broken - which is what this printer needs.
So being a "knows enough to be dangerous" amateur engineer - I decide I can make it better.
I thought a laser with a photocell would be a hell of a lot more accurate than an IR setup. In addition to being more accurate - adjusting a system with a beam you cannot see is hard - if it's aimed too high or low, you'll get different height readings if your object is closer to or farther from the sensor. With a laser I can actually see the beam is truly horizontal.
Would that provide greater accuracy? Can someone suggest a better/more accurate setup? I cannot have anything that physically touches the items on the tray - some items are light enough that merely brushing them will move them out of alignment. Sensing the actual height of the tray would be a possibility - but then you'd need to measure/know the height of the items on the tray. I'd prefer to keep the automated system as it is now and just replace the sensor with something more accurate.
So my current thought is a simple small photocell, one of these: https://www.sparkfun.com/products/8654 and an arduino to control the laser on/off as well as handle the photocell sensing and returning an on/off back to the main control board of the printer.
Anyone have a better idea?
Well mine was both not calibrated correctly upon receiving it, and as well, depending on the item you place on the bed - sometimes it would not read right. I had the print head hit a bottelcap I was printing on as the auto sensor did not work correctly.
I open the printer up and see the emitter is a BY500-TDT1 and the sensor is a BY500-TDT2. Looks like a simple infrared emitter/detector. Now, I dont have a camera capable of IR detection handy, but I'd venture to guess that the scatter of the infrared beam would not be overly accurate. Real great for sensing when the beam is broken, but real poor at sensing within 10ths of a mm when the beam is broken - which is what this printer needs.
So being a "knows enough to be dangerous" amateur engineer - I decide I can make it better.
I thought a laser with a photocell would be a hell of a lot more accurate than an IR setup. In addition to being more accurate - adjusting a system with a beam you cannot see is hard - if it's aimed too high or low, you'll get different height readings if your object is closer to or farther from the sensor. With a laser I can actually see the beam is truly horizontal.
Would that provide greater accuracy? Can someone suggest a better/more accurate setup? I cannot have anything that physically touches the items on the tray - some items are light enough that merely brushing them will move them out of alignment. Sensing the actual height of the tray would be a possibility - but then you'd need to measure/know the height of the items on the tray. I'd prefer to keep the automated system as it is now and just replace the sensor with something more accurate.
So my current thought is a simple small photocell, one of these: https://www.sparkfun.com/products/8654 and an arduino to control the laser on/off as well as handle the photocell sensing and returning an on/off back to the main control board of the printer.
Anyone have a better idea?