IR Emitter/Detector Circuit (Reflected Light Sensor)

I also wrote these requirements in a google doc file which might be easier to read: [login to view URL]

I am looking for someone to design two similar circuits dealing with emitting and detecting reflected IR light. Here are the deliveries for each circuit:

* Kicad files for the schematic and a PCB (no need to route wires on PCB since I will be modifying design to fit into a bigger project)

* A prototype of the circuit proving its operation (can either use the PCB or be hand soldered on a protoboard)

Payment Schedule:

* One-third of payment delivered when we agree on estimated power consumption, working distance, and you have told me the major components for each circuit. Basically this is a way to start payments to you before you do all the work, but I can also combine this with the other later payments if you want.

* One-third of payment delivered when the circuit is complete and working (you will send photo confirming and I’ll pay before you ship it to me)

* One-third of payment delivered when you are ready to deliver kicad files

The two circuits will be referred to as “Constant IR Circuit” and “Pulse IR Circuit”. The Constant circuit uses a constant IR LED and the pulse circuit pulses an IR LED at 38 Khz.

Here are some requirements for both circuits:

* Have a BOM cost of under $10 (I’m hoping for a BOM under $5 in quantities of 500).

* Both circuits should be powered by 3.3V and communicate with a microcontroller using 3.3V IO lines (Atmel Sam3x is the micro I’m using).

* Components should be available on Mouser or if there isn’t a reasonable option there then provide a link to some site where they can easily be purchased.

* Both circuits should reuse as many similar parts as possible.

* Both circuits should use SMD parts for the chips and passive components, but can use through hole parts for anything where through hole parts are better for cost/performance.

* There should be an easy way to adjust power going to IR LED (such as changing a resistor)

* There is a potentiometer to set a reference voltage used to detect when there is enough reflected light to output a high output.

* Consider the IR emitter and detector need to fit into a casing. This could be a T 1 ¾ LED or a plan to use an LED lens

* The lines coming from the microcontroller for each circuit should be:

** Vcc

** GND

** Signal (digital 0 or 3.3V signal the micro reads)

Constant IR Circuit Requirements:

* Voltage output of the IR detector should be amplified to make sensor sensitive.

* Compare the voltage from the amplified IR light to the potentiometer reference voltage and if it is lower “Output Signal” is near 0V and when IR light is reflected “Output Signal” is near 3.3V.

* The response time of this circuit should be under 1 microsecond.

* Range of this sensor must be 1-5 cm (though longer range is a bonus)

* Beam width should be at least 1 cm at 2 cm distance.

Pulse IR Circuit Requirements:

* Use something like a 555 timer (though feel free to use something else if you know a better option) to generate a 38 Khz pulse and blink the LED at that frequency

* Either use a IR detector pre-tuned to 38Khz or make a window filter to only pass this frequency.

* Voltage output frequency filtered IR detector should be amplified to make sensor sensitive.

* Compare the voltage from the amplified IR light to the potentiometer reference voltage and if it is lower “Output Signal” is near 0V and when IR light is reflected “Output Signal” is near 3.3V.

* Response time should be fast as is reasonable, but it’s understood it can’t be faster than 38Khz

* Range of this sensor would ideally be 10+ meters

* The only beamwidth requirement on this one is if we use a retro-reflector or separating emitter/detector then things should be reasonably easy to align.

Progettazione di Circuiti Microcontrollore Configurazione Circuiti Stampati

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