High! I have an old scanning spectrometer that goes from about 1900 to 9000 Angstroms. The scanning motor operates at 115VAC and can turn in either a forward or reverse direction. There are two switches, one at the low wave length end and one at the high wavelength end, which turn off the motor to keep it from ruining the mechanism. When the scanning motor moves from a higher wavelength to the lower shutoff point a red light turns on and the motor stops. When the scanning motor moves from the lower stop toward higher wavelengths the red light turns off and remains off until the scanning motor reaches the upper switch. At that point, the red light turns on and the motor is turned off. I'm using an TSL2561 light sensor and I want to use the lower switching point as a timing reference (start my Arduino program to log the light intensity from the sensor). I would like to monitor these two switches by using two analog (or digital) inputs to my Arduino Uno. I realize that I need a debounce circuit to handle the switch either turning on or turning off (depending on the rotation of the scanning motor). My question is how can I provide a compatible voltage to the Arduino Uno so that I can detect the state of the two switches? I have attached a PDF file which contains a schematic of the scanning motor circuit. Any suggestions please!!!
No PDF attached
Can you please tell me why my question was posted in the wrong place? I thought it was going to a forum on "General Electronics". Again, I apologize for my error.
pchemist:
Can you please tell me why my question was posted in the wrong place? I thought it was going to a forum on "General Electronics". Again, I apologize for my error.
This is a forum for Arduino and associated systems and if you are going to use an Arduino then this is the correct forum although Project Guidance may be a better place to ask. What makes you think that you have posted in the wrong place ?
NOTE : you have still not attached the PDF
Thank you for your reply. I don't have a problem with the Arduino Uno collecting data, I just have a question about how I can use the Arduino to detect the limit switches turning on or off. I don't want to place 115VAC across the input to my Arduino. Also, I thought I had attached the schematic! Here it is now! Thank you!
JA 82-000 SCHEMATIC.pdf (397 KB)
Are you willing and capable of modifying, tapping into, the wiring (viz. the limit switches)?
According to the schematic those limit switches are actually switching the full 115V AC. Better not mess with that.
DS1 is not a diode, it's some other kind of indicator light. I'd indeed go for a light sensor. The TSL2561 is an option, but as all you want to know is on or off I'd go for a much simpler solution: a phototransistor such as the TEMT6000 or a good old LDR. With a well chosen pull-up resistor (at least 10x the resistance of the sensor when the light is on - assuming it's well shielded from ambient so when lights off the resistance is at least 10x that resistor value) you can read them as digital inputs.
I think you can monitor the current end stop switches by using an AC opto coupler.
The component I used is a Fairchild FOD814A300. The output transistor will go right to an Arduino digital input.
You may have to reduce the 4.7µf capacitor. They are there to filter out the pulses from the optio output.
Also reducing the 121k will help as well.
