Hi,

I need to find a simple circuit diagram. I have been searching but the key words I can come up with only finds on/off circuits or transmitter and receiver circuits.

I would like to make an LED flash faster and faster the closer I put my hand to the IR receiver and Emitting diode (5mm).
Some might call it a combi of flashing LED and proximity sensor.

 

How do you expect to sense distance with that type of sensor / emitter? They are probably capable of binary determination of whether there is an object near them, but not an output proportional to distance.

You really need an IR or ultrasonic distance sensor for what you want to do.

Bob

 

Thank you for your reply. I expect the IR receiver to let through more voltage the closer my hand approaches the IR receiver and Emitting diode. This should make the 555 timer frequency faster.

 

I expect the IR receiver to let through more voltage the closer my hand approaches the IR receiver and Emitting diode.

Because of reflection from the emitter to the receiver, or because the receiver senses the heat of your hand?

The two solutions are very different, but both are more complex than you think they will be because the receiver will pickup IR energy from objects and people in the surrounding environment, the ambient air temperature, etc.

ak

 

IR receivers, use in TV remote controls, that I have seen have digital outputs. That might affect the ability to have the voltage change with proximity to the reflector. You might be better off using a photo transistor as the sensor.

 

Because of reflection from the emitter to the receiver, or because the receiver senses the heat of your hand?

The two solutions are very different, but both are more complex than you think they will be because the receiver will pickup IR energy from objects and people in the surrounding environment, the ambient air temperature, etc.

ak

thank you

Because if the reflection from emitter to receiver.

I think this circuit board works kind of the same way only without the comparator part?

 

I just realized that what I got is a IR emitter and not a photodiode which apparently is absolute not the same thing.

Is it just me or do they look the same?

 

A photodiode is not an emitter, it is a detector. The detector you showed is either a photodiode or phototransistor. The emitter is an LED.

An IR distance sensor operates by measuring the angle between transmitted and reflected beam. A proximity detector simply detects the presence of a reflection without an indication of distance.

Bob

 

Thanks

How do I see the difference between a white LED and a white photodiode? to me they look the same.

 

Yep, as do phototransistors. Hopefully, you know what you bought. Otherwise, you will have to test them to find out. I think the emitters are likely to be clear and the detectors be colored for filtering out visible light.

You really don't want a photodiode, they produce very low currents and need an opamp to make them do anything. You want a phototransistor.

Bob

 

Hi,

I need to find a simple circuit diagram. I have been searching but the key words I can come up with only finds on/off circuits or transmitter and receiver circuits.

I would like to make an LED flash faster and faster the closer I put my hand to the IR receiver and Emitting diode (5mm).
Some might call it a combi of flashing LED and proximity sensor.

View attachment 229518

you need to use something like this:
https://www.maxbotix.com/Ultrasonic_Sensors/MB1010.htm

it is a range finder and generates a voltage proportional to distance.

 

Hi,

I need to find a simple circuit diagram. I have been searching but the key words I can come up with only finds on/off circuits or transmitter and receiver circuits.

I would like to make an LED flash faster and faster the closer I put my hand to the IR receiver and Emitting diode (5mm).
Some might call it a combi of flashing LED and proximity sensor.

View attachment 229518

What you are looking for is a capacitive touch sensor circuit- the closer your hand is, the more capacitance (which you can measure) and then you can adjust the PWM to change the LED brightness.

PM me for a tutorial.

 

I am not sure I know the terms for what I need. As I understand, I would use the photodiode as a variable resistor in a 555 timer astable mode circuit. The more infrared light reflecting back to the photodiode the more voltage would run through it.

 

If you use a photodiode as a variable resistor in a 555 circuit you will be very disappointed, as a photodiode can produce very little current, and is not a variable resistor per se.

You will need to amplify the affect and use that to alter the 555 frequency. (I would suggest using an Op-Amp and the CV pin of the 555)

Or use a matching set of IR LED and photo-transistor instead.

 

This guy uses a photodiode with a opamp. To do that the photodiode must deliver a voltage to the opamp.

Isnt that possible to with a 555 timer in astable mode because of the very little current?