Basic distance emitor and receiver circuits

Thread Starter

q12x

Joined Sep 25, 2015
609
First, I have to mention that I am an artist and not an electronist. So my knowledge is limited in some directions of electronics.
I need a very basic (with minimum of components), very short range (~3 meters), (Like a remote control) emitor and it's receiver.
-It should not be with visible light since the entire panel is in direct light already both from natural and artificial light.
-I don't have IR Led's in stock. So it has to be with a coil of some sort.
-Ideally built with components that you have in stock ,the usual ones, and not very new or fancy that I have to wait 2 to 8 months to arrive.
A - Basic as to command a transistor that will command - a relay @5V /40mA /128R for the coil.
B - Basic as to command a transistor that will command - 5V to input pin5 for a LM3914.
Im not decided yet, and I might try both until I will decide which I will leave it as final.
This is just another module, for a bigger project im into.
Thank you for your immense help so far and happy holidays and happy new year 2021 !!!
 
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Thread Starter

q12x

Joined Sep 25, 2015
609
@AlbertHall Thank you for your response!
After your response, I changed the title and added a bit more description to my original text.
Because I was not that clear.
So I need a minimal way of switching a transistor from a small distance basically, through the air and not using any wires.
I don't have IR Led's in stock either. So it has to be with a coil of some sort.
 

AlbertHall

Joined Jun 4, 2014
11,309
That probably means an RF transmitter and receiver. The transmitter would be fairly simple coupled with perhaps a regenerative receiver as used to be used for model radio control.
 

djsfantasi

Joined Apr 11, 2010
7,689
Can it transmit sound? At ~3m, the volume can be reasonable. Then a burst at an audible frequency and level for a constant time could be detected. Add additional frequencies for specific periods to be more discerning.

Perhaps use a DTMF encoder/decoder chip...
 

Thread Starter

q12x

Joined Sep 25, 2015
609
Can it transmit sound? At ~3m, the volume can be reasonable. Then a burst at an audible frequency and level for a constant time could be detected. Add additional frequencies for specific periods to be more discerning.

Perhaps use a DTMF encoder/decoder chip...
Excelent idea and I thought at it as well. The problem is that I live inside an apartment and surrounded by neighbors with very sensitive (long) ears. The sound can be an ultra or infra sound, below or over the audible human range. It will wake up any animal if they have, but it will be for short time bursts.
I think at a resonable level, it can be a normal sound as well.... but in the 3 night/morning when all is quiet, ME pushing a screaming buzzer...that is hilarious.
Also, there is another impediment to sound. In the daylight, sometimes, I put music loud. Also there are all sort of sounds from all around that can potentially trigger the receptor. As you said, like a burst that will only be decoded, only in this case, then is fine. I never deal with bursts circuits like these before, though i know they exist.
I also thought about burst of light, like 4 times blips and also 4 leds on the receiver that will confirm each decoded step... but it is more complicated that I originally wish, with a nail long wire, a coil of some sort and a couple of passive components, that Ive seen in my youth but never retain the circuit.
 
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Thread Starter

q12x

Joined Sep 25, 2015
609
But what is the problem with a very short range radio frequency? I really dont know and i feel some defense from using it.
Or is more complicated to build than I imagined?
I already have in stock 2N7000 and 2N7002 mosfet transistors, which are basically sensing transistors, and I already used one on the same board, but for a close and manual use. Maybe with them I can make something for sensing some special waves from distance?
 
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Thread Starter

q12x

Joined Sep 25, 2015
609
Oh, silly me. I just remember that I have a couple of laser diodes. Maybe them can be of some use?
But I'm wondering if the normal daylight or artificial light can interfere. I imagine, a very dark transparent plastic, almost like glass used for welding masks, as a shield from general light, but laser to be able to penetrate it and activate the LDR on the other side? Also I'll have to snipe it very precisely as well.... Hmmm...
1608941507122.png
 

Thread Starter

q12x

Joined Sep 25, 2015
609
It's not difficult to harvest diodes from IR remotes, and receiver modules from junked AV gear.
I dont have that kind of stock or resources. I wish. I never worked with IR, or un-memorable few times.
Tell me, do I need a special receiver for an IR led, or is working fine with a LDR as well?
 

djsfantasi

Joined Apr 11, 2010
7,689
Excelent idea and I thought at it as well. The problem is that I live inside an apartment and surrounded by neighbors with very sensitive (long) ears. The sound can be an ultra or infra sound, below or over the audible human range. It will wake up any animal if they have, but it will be for short time bursts.
I think at a resonable level, it can be a normal sound as well.... but in the 3 night/morning when all is quiet, ME pushing a screaming buzzer...that is hilarious.
Also, there is another impediment to sound. In the daylight, sometimes, I put music loud. Also there are all sort of sounds from all around that can potentially trigger the receptor. As you said, like a burst that will only be decoded, only in this case, then is fine. I never deal with bursts circuits like these before, though i know they exist.
I also thought about burst of light, like 4 times blips and also 4 leds on the receiver that will confirm each decoded step... but it is more complicated that I originally wish, with a nail long wire, a coil of some sort and a couple of passive components, that Ive seen in my youth but never retain the circuit.

But with DTMF, the sound is audible and not disturbing to animals nor neighbors in short defined bursts. Pick up your phone and press the 5 button. That’s all that anyone would hear. As a mix of two frequencies, the sound would be specific and unlikely to be present accidentally. Which is why touch tone developers chose the frequencies to mix. A 5 mixed frequencies for 0.1 seconds ±10% would be unlikely to be present in the environment. Or the 123467890*# keys.
 

Thread Starter

q12x

Joined Sep 25, 2015
609
But with DTMF, the sound is audible and not disturbing to animals nor neighbors in short defined bursts. Pick up your phone and press the 5 button. That’s all that anyone would hear. As a mix of two frequencies, the sound would be specific and unlikely to be present accidentally. Or the 123467890*# keys.
I understand what you are saying but i never build something that will use this DTMF. It is very interesting concept, totally new to me, and some day I will try it, because it's very cool concept.
I also search about it just now and watch a short introduction on youtube.
I search for circuits and all i can find is 10 keys pad and they involve special IC or PIC. Hmmm....
I need something more simple but also safe from errors.
If you have a simple circuit that will make this DTMF, then is very fine with me, as long as I have the components.
DTMF decoder chip MT8870; so i'll have to wait 8 months for it to come. I want something to make until the end of year(in 5 days).
I will pass over this idea, with regret, because i like it.
I need something way more basic.
 
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djsfantasi

Joined Apr 11, 2010
7,689
I understand what you are saying but i never build something that will use this DTMF. It is very interesting concept, totally new to me, and some day I will try it, because it's very cool concept.
I also search about it just now and watch a short introduction on youtube.
I search for circuits and all i can find is 10 keys pad and they involve special IC or PIC. Hmmm....
I need something more simple but also safe from errors.
If you have a simple circuit that will make this DTMF, then is very fine with me, as long as I have the components.
DTMF decoder chip MT8870; so i'll have to wait 8 months for it to come. I want something to make until the end of year(in 5 days).
I will pass over this idea, with regret, because i like it.
I need something way more basic.
There is nothing simpler. Take the 10 key pad solution and simplify it to one key. And it will require a special IC. As would any solution. You could create a solution in, let’s say, 3 days.
 

Thread Starter

q12x

Joined Sep 25, 2015
609
@djsfantasi
DTMF decoder chip MT8870 will arrive in about 8 months if im lucky.
SO i'll need other ideas.
Thank you, you had a very original idea. I like it but i need to build it with what i have. It will remain as a plan B of course.
 

Thread Starter

q12x

Joined Sep 25, 2015
609
I look on another forum, from googling around and I answered myself.
The answer is : it is a very difficult subject. I did not remember to be, but ... it is.
Here is a compilation//I photoshoped some answers from that forum to give ME a good idea and a reminder in the future about this subject. I'm so disappointed. And I can see from the circuit, it is difficult to match the frequency as the author suggests. But I will probably try it since i have no other alternatives and it can be built with normal components that i have in stock.
If i will not be able to tune and find the frequency, then i will go to ebay variant, again, as plan B.
simple rf emitter receiver circuit copy 1.jpg
As a side note, on that forum I also find a link to this crazy list of RF circuits... but is a bit too much for me to build one. Too complicated for what i have in mind. But they are worth mentioning https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Homebrew_RF_Circuit_Design_Ideas.htm
 

Thread Starter

q12x

Joined Sep 25, 2015
609
Don't take me wrong. I am puting on the table everything I can think of. And the more ideas I have on the table , the better. So everything else you may think of, just put it here. It is welcomed.
I'm also thinking to go Back, to the idea with a signal light, like a pattern. The problem I have, is how to decode it?
 
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