# break-beam sensor to detect low paper supply [closed]

all. I know enough about soldering and circuits to be dangerous, meaning I can follow instructions, but I could not design my way through an open door.

I am interested in using an IR Break Beam Sensor (3.3v 20ma to power it--details https://www.adafruit.com/products/2167 ) to cause an LED to turn ON when the beam is detected, not when the beam is broken. Basically, I want to detect when a roll of paper is NOT between the two sensors and then have an LED stay on (or blink would be better). I should be able to do this simply, no? It needs to run 24/7 but the beam most of the time will not be broken. Any circuit guidance would be appreciated and then I will try to figure out what kind of battery power i would need. Oh, when the paper is replaced, I would want the circuit to turn off the LED. The paper is definitely thick enough to block the beam. Thanks for any guidance/resources. -Bob

## closed as too broad by Michael Karas, laptop2d, Autistic, brhans, ThreePhaseEelJan 10 '17 at 1:45

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Adafruit is helpful in that they have handy application guides for a lot of their products, including yours – Cheibriados Aug 12 '16 at 17:21
• @user2665119 you should do research BEFORE you ask questions here. electronics.stackexchange.com/help/how-to-ask – laptop2d Aug 12 '16 at 18:29
• I read adafruit's material. NONE of that material was helpful, so maybe you might want to read it as well before you comment. Thanks for your help. – user2665119 Aug 12 '16 at 20:09
• laptop2d, and how exactly do you know what research I did? You don't. If you have a suggestion, fine. But otherwise I fail to see any helpfulness from your contribution. – user2665119 Aug 12 '16 at 20:12
• VTC - This site is not a free consulting site from which to solicit designs. – Michael Karas Jan 9 '17 at 9:38

The 1k resistor sets the current through the LED (brightness). The current will be $$\frac{5V- V_{LED}}{R_{1k}}$$