Post by thread:EE: IR receiver with range >8m ?

hi, I have to know when something crosses 30 metres long line. If the distance was less than 8m, then I would use Everlight's IR receiver, ELIRM8601 for example (which responds to 38khz modulated IR signal). But I have to cover 30 metres. Any ideas? Laserdiodes? thanks, aadu adok -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> I have to know when something crosses 30 metres long line. If the distance was less than 8m, then I would use Everlight's IR receiver, ELIRM8601 for example (which responds to 38khz modulated IR signal). But I have to cover 30 metres. Any ideas? Laserdiodes? > Some modest lensing would almost certainly allow this - easily tried. Failing that, visible laser pointers would do it with ease, but visibility may not be what you want. That said, if the transmitter is recessed in a wider blackened housing and the receiver similarly, then it could be made that a laser dot would only be visible when you were being detected. If you don't want the red dot to give the game away as they walk through then IR is the way. Glass has varying attenuation at IR depending on composition but it would be easy to try some cheap glass lenses and see what happens - possibly at transmitter end only. The aim is to produce a parallel (more or less) beam of diameter equal to the lense diameter. An ordinary red high efficiency LED makes an extremely bright night time beam at tens of metres - an IR remote LED and lense should do similar. . RM -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

On Tue, 4 May 2004 10:37:30 +0300, you wrote: >hi, > >I have to know when something crosses 30 metres long line. If the >distance was less than 8m, then I would use Everlight's IR receiver, >ELIRM8601 for example (which responds to 38khz modulated IR signal). > >But I have to cover 30 metres. Any ideas? Laserdiodes? > >thanks, >aadu adok Laser diodes will probably not help - you get more overal power from IR diodes. Some powerful IR LEDs and some reasonable optics to narrow the beam and the receiver's field of view should get you the range you need, but it will need solid mounting to keep it aligned. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Why don't you just go with RF? Is there some reason you absolutely have to use IR over such a great distance? Aadu Adok wrote: {Quote hidden}> hi, > > I have to know when something crosses 30 metres long line. If the > distance was less than 8m, then I would use Everlight's IR receiver, > ELIRM8601 for example (which responds to 38khz modulated IR signal). > > But I have to cover 30 metres. Any ideas? Laserdiodes? > > thanks, > aadu adok > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> Why don't you just go with RF? Is there some reason you absolutely have > to use IR over such a great distance? Read again and you'll see that it's a "break the beam" 'intruder' detection system. RF could be used, but in a different mode (eg radar) > > I have to know when something crosses 30 metres long line. If the > > distance was less than 8m, then I would use Everlight's IR receiver, > > ELIRM8601 for example (which responds to 38khz modulated IR signal). > > But I have to cover 30 metres. Any ideas? Laserdiodes? -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

Crap, missed that part of the email. If it's an intruder detection system, I would use a laser, or even directional IR module made for such a purpose (has been mentioned). A laser based system is going to much more effective than an IR based system and you can bounce the beam around using simple reflectors. -Shawn Russell McMahon wrote: {Quote hidden}>>Why don't you just go with RF? Is there some reason you absolutely have >>to use IR over such a great distance? > > > Read again and you'll see that it's a "break the beam" 'intruder' detection > system. RF could be used, but in a different mode (eg radar) > > > >>>I have to know when something crosses 30 metres long line. If the >>>distance was less than 8m, then I would use Everlight's IR receiver, >>>ELIRM8601 for example (which responds to 38khz modulated IR signal). >>>But I have to cover 30 metres. Any ideas? Laserdiodes? > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> A laser based system is going to much more effective than an IR based > system and you can bounce the beam around using simple reflectors. > > -Shawn howdy, as lasers use visible light (650nm), what would you use for detecting part? typical photo-diode? how does it make a difference if ligth is coming from laser or from sun? by filtering? thanks, aadu adok -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

On Wed, 5 May 2004 11:59:14 +0300, you wrote: >> A laser based system is going to much more effective than an IR based >> system and you can bounce the beam around using simple reflectors. >> >> -Shawn > >howdy, >as lasers use visible light (650nm), what would you use for detecting >part? typical photo-diode? Yes. >how does it make a difference if ligth is >coming from laser or from sun? by filtering? By optics - put the detector down a tube, so it only sees light from a specific direction. Also, using a modulated beam and AC amplifier will filter out any ambient light effects.. -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

>>as lasers use visible light (650nm), what would you use for detecting >>part? typical photo-diode? >Yes. >>how does it make a difference if ligth is >>coming from laser or from sun? by filtering? >By optics - put the detector down a tube, so it only sees light from a specific direction. >Also, using a modulated beam and AC amplifier will filter out any ambient light effects.. Let me push the IR receiver barrow again again again. IF the IR receiver works OK its going to be far far easier than rolling you own with a laser. It's easy to try the IR receiver, it's cheap enough, and if it doesn't work then by all means move onto a laser and PIN diode (or similar) receiver. Making receivers work well in sunlight is a non trivial task (based on my experience). Shielding the receiver down a longish tube certainly helps. IR filters don't help much against sunlight as the sun has the original patent on IR transmission and lets you know it. You can make detector circuits which dynamically bias themselves to allow for "DC" light levels but they are not without their problems. You then have to modulate the laser and make an Ac receiver and amplifier and detector and .... . The IR receiver module has thus inside it already. TRY and IR receiver with a lense and a remote. See how far you can get. IF that's not enough, try a lense at both ends. (Or do a little theory to see how good it should be.) IF the IR receiver doesn't work, then make life difficult for yourself and use a laser. Russell McMahon -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

> Let me push the IR receiver barrow again again again. > IF the IR receiver works OK its going to be far far easier ok. let's see if I got it right: * turn IR led on/off every 13us (to get 38khz) * receive modulated beam with IR receiver module (TSOP, ELIRM8601, etc.. with TTL level output) * if the beam is uninterrupted, there will be logical 1 on receiver output * if the beam is broken, there will be 0 on receiver output or am I missing something? thanks, aadu adok -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

{Quote hidden}> >-----Original Message----- >From: Aadu Adok [Aadu.AdokEraseME.....HANSA.EE] >Sent: Wednesday, May 05, 2004 8:21 AM >To: EraseMEPICLISTMITVMA.MIT.EDU >Subject: Re: EE: IR receiver with range >8m ? > > >> Let me push the IR receiver barrow again again again. >> IF the IR receiver works OK its going to be far far easier > >ok. let's see if I got it right: > >* turn IR led on/off every 13us (to get 38khz) >* receive modulated beam with IR receiver module (TSOP, ELIRM8601, etc.. >with TTL level output) >* if the beam is uninterrupted, there will be logical 1 on receiver >output >* if the beam is broken, there will be 0 on receiver output > >or am I missing something? > >thanks, >aadu adok > Not quite.. I have used a few different brands of IR receiver, and have found: 1.You'll get a high signal when clear, and a low signal when IR is present. i.e. an active-low signal. 2.Just modulating at 38 khz is not enough, constant 38Khz will only give a brief active signal.. the flashing will have to be gated with a slower pulse to give a matching (inverted) output at the receiving end. If you read the datasheet of the receiver carefully, this information is usually included there. Good Luck, Lyle -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu

> * turn IR led on/off every 13us (to get 38khz) > * receive modulated beam with IR receiver module (TSOP, > ELIRM8601, etc.. > with TTL level output) > * if the beam is uninterrupted, there will be logical 1 on receiver > output > * if the beam is broken, there will be 0 on receiver output > > or am I missing something? Yes, the requirement that the modulation has periodic breaks, for instance a 500 Hz on/off. See datasheets (as always). Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu

part 1 1786 bytes content-type:text/plain; (decoded 7bit) ok. let's see if I got it right: * turn IR led on/off every 13us (to get 38khz) * receive modulated beam with IR receiver module (TSOP, ELIRM8601, etc.. with TTL level output) * if the beam is uninterrupted, there will be logical 1 on receiver output * if the beam is broken, there will be 0 on receiver output or am I missing something? It's very slightly more complex than that. Most IR receivers (certainly all I have seen) require the 38 KHz to be 'modulated' to maintain lock. So if you eg turn the 38 kHz on and off at a slower rate (eg 1 kHz) then the output should be a 1 kHz square wave. If you just send "DC" (ie permanent 38 kHz) the receiver output reacts as if there is no signal. NBNBNB This behaviour is not in any data sheet I have seen (although it may be in some I have not seen ;-) ) - I guess they assume people will be sending data of some sort. Also, the sending signal to the LED does NOT have to be a 38 kHz square wave - it can be shorter bursts of IR energy at a 38 kHz rate. This allows you to send a LARGE pulse to the LED and then leave it off for the remainder of the 26 microsecond frame and cool down and recover its breath. This allows a much larger effective energy input as the systems tends to care only that it has seen "something" each 26 uS period or not. Presumably there is some lower time limit that the receiver needs and presumably this is (possibly) in the data sheet. Starting with 50/50 can't hurt. I've attached some IR receiver circuits that Jinx provided just to lure you to the dark side. Don't do it though - use a commercial module :-) Russell McMahon -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu part 2 4753 bytes content-type:image/gif; (decode)

On Wed, 5 May 2004 15:20:56 +0300, you wrote: >> Let me push the IR receiver barrow again again again. >> IF the IR receiver works OK its going to be far far easier > >ok. let's see if I got it right: > >* turn IR led on/off every 13us (to get 38khz) >* receive modulated beam with IR receiver module (TSOP, ELIRM8601, etc.. >with TTL level output) >* if the beam is uninterrupted, there will be logical 1 on receiver >output >* if the beam is broken, there will be 0 on receiver output > >or am I missing something? Probably. The reason for saying 'probably' rather than 'yes' that is that some IR receiver modules need to see a modulated carrier for best performance, so I'd reccommend modulating the 38KHz at around 1KHz, i.e. a 1ms burst of 38khz, a 1ms gap etc. This would give a 1KHz squarewave when the beam is intact, and a logic high when no beam is present. This could be done in one chip with a 556. -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspamspamBeGonemitvma.mit.edu

>Read again and you'll see that it's a "break the beam" 'intruder' >detection system. RF could be used, but in a different mode (eg radar) Microwave barriers work fine over such distances (and much greater than that). The available gain at the receiver is much larger and the transmitter and receiver are on opposite sides, not on the same (as in radar). Peter -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu