Help for a dummy

[timothyjackson]

Background: I am getting more and more into the world of electronics, really opeing my eyes to the huge potentials of circuit design.

However: I appear to be stuck.

I would like to create the simplest circuit:

Spec: To control an LED using infrared. That is, imagine an led two metres away from you; i would like to turn this on using a simple infra red emitter.

Would really appreciate a little guidance.

Best regards

Timothy
tim@au-my.com

 

[lavenatti]

Try doing a search for schematics for a TV remote control tester. This will do what you're looking for.

 

[timothyjackson]

yeah...ive already found some circuits, but, they all look far too complicated for the application i'm after, that being, turning an led on and off.....still....thanks for your advice my friend...

 

[zachtheterrible]

How do you want to control it? Like a tv remote works, or just simply want it 2 turn on by the amount of IR light that falls on it? The latter would be extremely simple, but would not work well if there's too much ambient light. and dont b so hard on urself . . . ur not a dummy :lol:

 

[timothyjackson]

hello zachtheterrible

thanks for your reply. Really appreciate it.

Becuase I'm not ofay with electronics terminology I shall describe physical actions.

Press button which emits IR to the led circuit.
This turns on the led (2 metres away for example)
To turn it off, press the emitter button, the ir beam turns off the circuit.

So i guess, "to turn on and off the circuit using IR light emitted from the transmitter" button would be a better answer.

Hope to hear from you.

Timothy

 

[timothyjackson]

.....check this circuit out...

www.hut.fi/Misc/Electronics/circuits/irdetector.html

Can i amend/add/change this so the led stays on when the ir signal is recieved, and only turns off when recieving the ir signal again...and so on?


:?: :?:

 

[zachtheterrible]

Yeah. do u know what an SCR is? When a signal is received @ the base of the scr (i dont know if im using the correct terminology, im just gonna treat the scr like a regular ol' transistor) it will let current run through the collector 2 the emitter. As long as this current runs through, the scr will stay on. if the current through the scr is interrupted, the scr will turn off. Thats the hard part. I think i have an idea, but i doubt that itll work.

Could someone else tel me if this is a good idea?: What i was thinking is just having an emitter follower circuit that turns off when it detects IR light where "circuit that interrupts current flow when it detects light" is.

I think if you're only 2 meters away from the circuit, it shouldnt be affected too adversly by ambient light, but im not sure. ive never done an IR circuit. hope this helps

 

[lavenatti]

Might be easier if each pulse of light triggered a toggle type flip-flop.

 

[timothyjackson]

hello zachtheterrible & lavenatti

Thanks for yout time and effort. REally appreciate it.

I don't know what an SCR is, but it shouldn't be difficult to find out.

So zachtheterrible, what your saying is, with your circuit, each time the reciever IR led receives a pulse from the Transmitter, and this runs through to the SCR it will change the state of the scr to allow current to flow to the LED? And vice versa, by interupting the SCR again, the state will be changed to cut off the circuit to the LED?

If so it sounds perfect, and, whats more "simple"

Hello lavenatti, I like your idea too, and I've been researching flip flop circuits/IC's. I've come very close to using a 555, but I can't work out how to wire/connect up the pins so that it actually "latches"....currently it sned sout an ocsillating output.

I must say, I'm really enjoying learning all this. Fantastic.

Thanks guys.

 

[Nigel Goodwin]

So zachtheterrible, what your saying is, with your circuit, each time the reciever IR led receives a pulse from the Transmitter, and this runs through to the SCR it will change the state of the scr to allow current to flow to the LED? And vice versa, by interupting the SCR again, the state will be changed to cut off the circuit to the LED?

An SCR (Silicon Controlled Rectifer) can only be turned ON, not OFF, to turn it off the current passing through it has to drop below it's 'holding current', when it automatically switches OFF.

Also these crude schemes with a photo-transistor aren't going to be very reliable - they will be triggered by ANY IR source near by, and also by visible light. It's usual (for good reason) to use a modulated IR beam, the receiver then detects the modulation - again, usually, some kind of coding is carried on the modulation as well - in order to differentiate between different buttons and different remotes.

The simplest way is to use a standard IR receiver IC, as used in TV's etc. Then modulate your transmitter at about 38KHz, the output of the receiver IC goes LOW when it detects the 38KHz IR signal. This overcomes the ambient light problems, but still means that ANY IR remote control will trigger your device.

To cure that problem you can add coding, using either micro-controllers or specific chips (actually pre-programmed micro-controllers). This makes the circuit nice and simple, including the latching if you use your own micro-controllers - my PIC tutorials include this very subject, turning LED's ON and OFF via IR, using both seperate ON and OFF buttons, and a single button which toggles the output.

 

[timothyjackson]

Hello Nigel Goodwin,

3 things for you kind sir.

1 - Your nickname is fantastic. I love it
2 - thanks for your advice, I will need a little tie to digest it.

So far I understand your point about coding the IR signals, so that, the LED does what I want it to do, when i want it done. I was going to be using specific frequency IR transmitters and receivers, with ambient light filters? will this not cure the problem?

3 - With PIC's... am i required to purchase software which "programmes the chip"... this would be a simpler option, but how much would it cost...

Rgds

timbo

 

[Exo]

I was going to be using specific frequency IR transmitters and receivers, with ambient light filters? will this not cure the problem?

You can't use a filter to prevent triggering from ambient light. There is some degree of IR in abmient light that makes it trigger. If you were to filter this out then you would also filter out the IR sent by the remote.

3 - With PIC's... am i required to purchase software which "programmes the chip"... this would be a simpler option, but how much would it cost...

For programming pic's you will need a pic (obviously), a programmer (wich is cheap to build), programming software (winpicprog by Nigel is free) and a compiler (free from microchip).
The software that gets uploaded to the pic you gave to write yourself.

 

[Nigel Goodwin]

So far I understand your point about coding the IR signals, so that, the LED does what I want it to do, when i want it done. I was going to be using specific frequency IR transmitters and receivers, with ambient light filters? will this not cure the problem?

Ambient light filters REDUCE the ambient light, they don't block it, so they only improve the problem a little - most IR photo-transistors already include filtering in their encapsulation.

Using very narrow band filters and accurately tuned transmitters would work, but it's a very 1970's solution, and would be fairly complicated and expensive. Remote control has moved on a great deal since those old crude days!.

3 - With PIC's... am i required to purchase software which "programmes the chip"... this would be a simpler option, but how much would it cost...

All the required software is free!, you only need a PIC programmer, you can either buy one, build one from a kit, or build one from scratch. If you want to build one from scratch I recommend the P16PRO40, you can find the circuit on my website - although you can buy these very cheaply as a kit, so it's not worth buying the parts seperately.

 

[zachtheterrible]

well ill let y'all take it from here. i didnt know timothyjackson knows as much as he does :lol:.

 

[timothyjackson]

Hello Nigel,

Once again, thankyou very much for your time and information.

Can you recommend somewhere to buy the PIC programmer?

I'm going to take some time and look at your website, and, print out your advice and begin some PIC work.

Many thanks

Timbo.

 

[Nigel Goodwin]

Can you recommend somewhere to buy the PIC programmer?

You've not filled your location in, so I've no idea where you are?.

 

[timothyjackson]

sunny england.

 

[Nigel Goodwin]

sunny england.

I know where England, but I'm not sure about 'sunny england'!.

Try Quasar Electronics, they have the P16PRO40 at a good price - it's well worth while spending the extra for a ZIF socket, I wouldn't be without one!.

 

[timothyjackson]

"I know where England, but I'm not sure about 'sunny england'!."

Now you know why i wasn't worried about the ambient light issue.


Thanks Nigel, will check it out.

Timbo