Laser emitter and receiver

Hello everyone, I'm doing a circuit with an infrared laser emitter and a receiver. However, I have had problems with sunlight because it produces erroneous readings on the receiver. I understand that with a filter I can fix this, can someone help me with the design of this filter or can you give me information about it?

Thank you very much

Hi, and welcome to the forum.

Remote controls use modulated infrared light for those reasons. And a receiver with a narrow bandfilter and gain control.

So why a laser? Leo..

I recently did a project for reading my electricity meter. The thing is an old ferrarismeter with a moving wheel that has a mirror strip on it's side and has a 1 cm black bit. https://www.google.be/search?q=ferrarismeter&tbm=isch

I started off , as many do with a tracking sensor

|500x500

Now I understand that for many people who have a meter with a clear plastic casing where the rotating disc turns close to that casing this works perfectly fine. For me it did absolutely nothing.. My rotating disc is quite small and located about 10 cm behind the casing. And my casing is tinted brown..

So i ditched the tracking sensor for an obstacle avoidance sensor which is basically the same thing but a bit more powerful. |500x246

That thing aged me by 10 years in a month. if positioned and tuned (took hours each time) just right it would work for about a day. I ended up making at least 10 casings , fixtures rests in plastic , puttyy , cardboard duct tape , etc etc.. the longest it lasted without crapping out was 3 days.

I tore off the whole thing and am now using an actual red laser emitter and a photoresistor on an analog input pin. ( this time on an arduino instead of straight on my raspberry pi's digital pin) |500x500 |500x500

for the photo resistor I used a piece of rectangular dark plastic where I drilled a hole in , glued a small dice sized block of wood next to it and put the sensor on that. the laser shines on the wheel and the reflection is a bright line. The photo resistor on the analog pin reads about 200 when lit, about 600 when the laser goes over the dark spot.

I also had to tape over the transparent parts of the meter because the thing sits close to the garage door. When the garage opened sunlight would interfere. Which did not happen for the IR sensor though.. Still . The laser saved my life. It's way more robust than using an IR sensor/receiver.

Without knowing the details of your project this is the best reply I can give that's related.

Good luck.

sbarahona: Hello everyone, I'm doing a circuit with an infrared laser emitter and a receiver. However, I have had problems with sunlight because it produces erroneous readings on the receiver. I understand that with a filter I can fix this, can someone help me with the design of this filter or can you give me information about it?

Thank you very much

You didn't say which emitter and receiver you have, you didn't say whether you mean optical filter or modulation filter.

A laser diode takes a special power supply that monitors the laser's output from the laser's 3rd pin in a feedback-loop. And most cheap laser power supplies are not designed to be modulated. So... it's note easy to build a laser transmitter, and a laser pointer usually won't work.

I understand that with a filter I can fix this

A filter may help, but it won't help if sunlight is directly (or sometimes indirectly) hitting the receiver. Sunlight is broadband and it certainly contains the same wavelengths as your transmitted light.... You probably need a black tube (and maybe some lenses if you can figure out the optics) so that only light directly from the transmitter hits the receiver.

"A laser diode takes a special power supply that monitors the laser's output from the laser's 3rd pin in a feedback-loop. And most cheap laser power supplies are not designed to be modulated. So... it's note easy to build a laser transmitter, and a laser pointer usually won't work. "

Uh,,, Well,,, Not really. Most semiconductor LASER diodes in use today do not even use (a lot do not even have) the feedback diode (pin 3 is NC). Semiconductor LASER diodes DO, however, require 'Constant Current Regulated' power supplies to operate reliably over full lifetime (don't like power spikes, and heat build up from too high a drive current), but are easily TTL modulated.

You usually get easier alignment and better performance in IR Light Comm.s using IR LED emitters and amplified photo-diodes. Modulated xmit, of course.

Can you show a picture of what you are doing ?

It does sound like you are trying to read the rotation of an old metal dial meter without interfering with the meter. Can you confirm this ? In this case the solution may be optical , requiring the use of lenses.

sbarahona: Hello everyone, I'm doing a circuit with an infrared laser emitter and a receiver. However, I have had problems with sunlight because it produces erroneous readings on the receiver. I understand that with a filter I can fix this, can someone help me with the design of this filter or can you give me information about it?

Thank you very much

Sorry i read subsequent posts. What are you trying to do ?

@Boardburner2

My ferrarismeter issue is solved :) no worries.

I wrote about my recent experiences with IR transmitters/receivers & lasers in the hopes OP would be able to pick something up from it.