IR Circuit Help, WAS: Battery Power Supply Help

[Nigel Goodwin]

One last question... shouldn't I have a diode between Vreg and the capacitor, to keep it from discharging into the rest of my circuit, 1A would toast my uC's...

No need, current doesn't just flow anywhere, only where it's required, in this case through the LED.

 

[Gandledorf]

One last question... shouldn't I have a diode between Vreg and the capacitor, to keep it from discharging into the rest of my circuit, 1A would toast my uC's...

No need, current doesn't just flow anywhere, only where it's required, in this case through the LED.

Thank you very much! You have been so helpful in this project. My last question would be: Do you know where one can buy a MAX603 (I've checked all the spots I know: jameco.com, futurlec.com, mouser.com, digi-key.com), or know of another good switching regulator, preferably one without an inductor, as I have had bad luck making my own.

EDIT: BTW, I can't easily use two LED's at low cost, due to the fact that I am collimating the light through a DCX lens due to the long distances involved.

 

[Nigel Goodwin]

Thank you very much! You have been so helpful in this project. My last question would be: Do you know where one can buy a MAX603 (I've checked all the spots I know: jameco.com, futurlec.com, mouser.com, digi-key.com), or know of another good switching regulator, preferably one without an inductor, as I have had bad luck making my own.

Sorry I don't, I would have thought that the USA would be a better bet than the UK - I presume you are in the US from the companies you mentioned?.

EDIT: BTW, I can't easily use two LED's at low cost, due to the fact that I am collimating the light through a DCX lens due to the long distances involved.

Right, one little thought though - I presume you do know that IR is focused differently than visible light?. It's not really a problem these days, you can simply use a cam-corder to set the focus (they see IR).

 

[Gandledorf]

Sorry I don't, I would have thought that the USA would be a better bet than the UK - I presume you are in the US from the companies you mentioned?.

Yes, unfortunately Do you know of any other good switching regulators? What do you typically use in your PSU's?

EDIT: BTW, I can't easily use two LED's at low cost, due to the fact that I am collimating the light through a DCX lens due to the long distances involved.

Right, one little thought though - I presume you do know that IR is focused differently than visible light?. It's not really a problem these days, you can simply use a cam-corder to set the focus (they see IR).

Yeah, already knew about the trick, also works with a digital camera. Thats how I plan on sighting the devices. Kind of a neat thing to discover, I found it purely on accident when taking a photo of a working circuit.

I think you've convinced me to use a detector module, one question though, where did you buy the model you have on your site? I can't seem to find them anywhere.

Here is my circuit, modified again to account for a status LED, I go ahead and use the same signal as you ought to be able to see it light up I know I should probably change the resistor in series with the status LED, to make it brighter.

**broken link removed**

 

[Nigel Goodwin]

Yes, unfortunately Do you know of any other good switching regulators? What do you typically use in your PSU's?

I usually use 7805 or 78L05 :lol:

To be honest, I wouldn't worry about it for now, you have a lot of work to do - I would breadboard a prototype (using a 7805) and get the rest working first. Once it's all working, you can measure consumption, and then design the PSU accordingly.

I think you've convinced me to use a detector module, one question though, where did you buy the model you have on your site? I can't seem to find them anywhere.

The one I use I obtained as a spare part, it's actually used in various Tatung and Grundig TV's - as it's a european part you will probably struggle in the states. From what I've heard, even Radioshack stock IR receivers - the particular type doesn't really matter, as long as you tune your modulation frequency to that of the receiver, this gives maximum range. Most are about 38KHz, although they can vary from about 36-40KHz. I noticed one in a TV/DVD today, it was only 1/4 inch square, if you are wanting small - that's the sort of thing to be looking for.

Here is my circuit, modified again to account for a status LED, I go ahead and use the same signal as you ought to be able to see it light up I know I should probably change the resistor in series with the status LED, to make it brighter.

Why waste an extra transistor and resistors?, simply connect the visible LED, and it's series resistor, from the collector of the existing transistor to +5V - in parallel with the IR one and it's resistor.

 

[Gandledorf]

I usually use 7805 or 78L05 :lol:

To be honest, I wouldn't worry about it for now, you have a lot of work to do - I would breadboard a prototype (using a 7805) and get the rest working first. Once it's all working, you can measure consumption, and then design the PSU accordingly.

True, I am probably getting ahead of myself in that respect. It just seemed like something I could do now, while waiting on the parts I need, which might take a month or so.

The one I use I obtained as a spare part, it's actually used in various Tatung and Grundig TV's - as it's a european part you will probably struggle in the states. From what I've heard, even Radioshack stock IR receivers - the particular type doesn't really matter, as long as you tune your modulation frequency to that of the receiver, this gives maximum range. Most are about 38KHz, although they can vary from about 36-40KHz. I noticed one in a TV/DVD today, it was only 1/4 inch square, if you are wanting small - that's the sort of thing to be looking for.

I take a look and see what I can find. How hard is it to have several of these recievers feeding the same input line?

Why waste an extra transistor and resistors?, simply connect the visible LED, and it's series resistor, from the collector of the existing transistor to +5V - in parallel with the IR one and it's resistor.

Good idea, I'm just used to making things as modules. One last question, when determining the current over the LED, how do the currents scale? I'm using a BVT-529TT3 as my visible light LED, it's rated at 7800mcd, 30mA continuous forward current, and 160mA max forward current (10% duty cycle, 0.1ms pulse width). How does this scale? Can I simply assume linearly?

 

[Nigel Goodwin]

I take a look and see what I can find. How hard is it to have several of these recievers feeding the same input line?

They usually have an open-collector type output, which (thanks to info given on this BBS!) usually has a high value pullup resistor internally. I should check the ones you eventually get, but the open-collector outputs let you simply parallel them.

I've never done this - but I seem to remember I've seen it done somewhere - again, experimentation is the key.

 

[Gandledorf]

I've located a number of parts through mouser that look like they'd work. My problem is I am having trouble determining which one will work best. I've decided to try and go with a 56kHz carrier wave, and so I am looking at the 56kHz reciever units by Vishay Semiconductor. Here are the parts and data sheets:

TSOP1256
**broken link removed**

TSOP4856
**broken link removed**

What kinds of things should I use to decide which to use? Are these suitable?

 

[Nigel Goodwin]

I've located a number of parts through mouser that look like they'd work. My problem is I am having trouble determining which one will work best. I've decided to try and go with a 56kHz carrier wave, and so I am looking at the 56kHz reciever units by Vishay Semiconductor. Here are the parts and data sheets:

What kinds of things should I use to decide which to use? Are these suitable?

They look fine, interesting reading about the sort of signals they will work with - sounds familiar doesn't it :lol:

Purely as a matter of interest, what made you choose to go with the 56KHz ones?. I don't see that it will make much difference which ever one you choose, presumably you have a reason? (one of which might be that most TV remotes don't work that high).

 

[Gandledorf]

They look fine, interesting reading about the sort of signals they will work with - sounds familiar doesn't it :lol:

That it does

Purely as a matter of interest, what made you choose to go with the 56KHz ones?. I don't see that it will make much difference which ever one you choose, presumably you have a reason? (one of which might be that most TV remotes don't work that high).

Well the reason is kind of two fold. First off, for my environmental application, there is no reason, the reason solely revolves around my secondary project, the ir tag set. First off, remotes not working that high helps to some degree, second, the old WoW tag sets ran off a 1.8kHz signal on a 56.7kHz carrier wave, so using a 56kHz carrier wave in my project gives me the option of later setting a compatibility mode on my device.

Another question: For the environmental application, we aren't transmitting data, but rather trying to measure the level of transference of light. Is a detector unit like this going to force output to either 0V or 5V, or will I still get a steady signal from 0 - 5V which I can then feed to an ADC to obtain a level of transference?

 

[Nigel Goodwin]

Another question: For the environmental application, we aren't transmitting data, but rather trying to measure the level of transference of light. Is a detector unit like this going to force output to either 0V or 5V, or will I still get a steady signal from 0 - 5V which I can then feed to an ADC to obtain a level of transference?

The IR receivers output a pure logic signal, high for no carrier detected, and low for carrier detected - you can't measure strength at all, except if they are within range or not.

To measure light strength you are going to need an analogue system.

 

[Gandledorf]

The IR receivers output a pure logic signal, high for no carrier detected, and low for carrier detected - you can't measure strength at all, except if they are within range or not.

To measure light strength you are going to need an analogue system.

So to measure strength for my environmental app, I should go with the approach of bandpass and op-amp, right?

 

[Nigel Goodwin]

The IR receivers output a pure logic signal, high for no carrier detected, and low for carrier detected - you can't measure strength at all, except if they are within range or not.

To measure light strength you are going to need an analogue system.

So to measure strength for my environmental app, I should go with the approach of bandpass and op-amp, right?

As you're wanting to measure both signal strength, and detect a unique ID, I would suggest an AGC amplifier and bandpass filter - that way you can use the AGC line for an indication of signal strength, and it will work over a wide range. A PLL at the output can still be used to detect the modulation frequency.

Do I recall correctly that this was for use underwater? - how does IR travel underwater?, it's not something I've ever looked into.

 

[Gandledorf]

As you're wanting to measure both signal strength, and detect a unique ID, I would suggest an AGC amplifier and bandpass filter - that way you can use the AGC line for an indication of signal strength, and it will work over a wide range. A PLL at the output can still be used to detect the modulation frequency.

Do I recall correctly that this was for use underwater? - how does IR travel underwater?, it's not something I've ever looked into.

I think right now we're scrapping the unique ID portion, and considering sending it on a separate digital channel. I.E., it will transmit through one emitter an analog signal for % transference, and then the ID on across another emitter modulated at a different frequency.

Yes it will be used underwater, I am not sure exactly what the properties are, but I do know that in our proof of concept, we were able to detect a continuous beam across a pool of clear water with no difficulties for the distances in mind.