555 Sanitizer Dispenser (With cut-Off)

The old circuit v1 is based on 555 IC, for which needs more discrete components and can't connect the IR diode / photo diode directly without an amplifier.

So, if an amplifier is used cheapest one available is an LM325, which is a dual OpAmp package, so instead of using a 555 to create a single pulse / one shot / monostable circuit. The same can be achieved using an OpAmp.

OPAMP 1 : Sensor / Signal amplifier.

OPAMP 2 : Monostable / One Shot circuit.

So, whoever wanting to create a project using these circuits, please wait for V2 of circuit, which will b cheaper and more reliable.

IR sensor modifications : When white paper is placed at about 0.5cm, transistor gets 0.56v just enough to trigger it.

but when a human hand is placed at same distance or even near, the photodiode output voltage doesn't rise above 0.42v as shown in pic.

the 222n transistor used requires min 0.55 / 0.6v at base to switch it ON.

solutions:
* run the circuit at higher voltage (currently testing at 5v)
* search for alternate transistor with lower min base voltage ( should be cheap and widely available)
* try adding more IR emmiters / LED around the photo diode, possibly increasing photodiode output.

will further test with given solutions.

working for white objects, but doesn't work for hands (IR sensor)

Designing the final circuit for simulation and layout. 1. adding auto put-off timer using RC pair in series with trigger input. 2. modifying circuit to use any generic IC pair as proximity sensor will soon upload LTspice simulation and KiCad design files.