In-between cirsuits can be found on Rob Paisley's site. One key to blocking interference is to actually modulate the IR beam. It still won;t work if ambient sources completely swamp the detector, but if the detector only responds to a singla that pulses at some frequency other than AC line frequency, it can discriminate between the actual emitter and ambient light sources with IR content.
Yes, more complex, but still well within the realm od DIY, and not as complex nor as expensive as the Logic Rail circuits.
For the original purpose, in a hidden staging yard, this circuit is plenty adequate. No need to be complex where it is not needed. The simpliest solution, for a given situation, is usually the best.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thank you Dave for your interest in working with “Inexpensive infrared train detector circuits”. The idea is basically any low cost IR circuits that operates only an LED. Both of these circuits do operate and LED base on the change in the IR light level. The NPN Phototransistor IR can be built to be very sensitive to any form of IR light. When the IR light gets between the cars, you can see a change in the LED level.
In my MR Oct. 2009 article there were a Red and a Yellow, LED in a low light staging area. When the train came in to a single ended staging track, the Yellow came on then the Red. The LEDs would flicker as the train passed through. Then you stop on Red only! On backing out, if the Red went out, you are going in the wrong direction. The two IR sensors, under the track, were about 2 inches apart. A Diode Emitter makes a strong IR light at 40 ma. If you use two of these in series, then you need only one 180 ohm 0.5 W resistor for 12 VDC.
Logic Rail Technologies has more electronic in their product to reduce any problems for other IR light sources. They have 2 or 4 second detector release time to eliminate any flickering. They have screw terminals for inputs and outputs that can control other electronic devices.
To some people time is money, and they can have a complete Model Railroads built for them.
Dave, I know you have started a thread on this subject, and the number of your viewers has become very large. I hope you keep it going at: http://cs.trains.com/mrr/f/744/t/213706.aspx
Bob Frey
Website: http://bobfrey.auclair.com
Bob
Thanks for the updated circuits.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
The circuit for inexpensive infrared train detector was first published in MR in the October 2009 issue. The “K” for a resistor on the Darlington was missing, so that circuit as printed would not work. (It was corrected later.) Another problem was that about 1 year later, the QRB1114 IR Reflective Sensor became obsolete. About two year latter the IR Diode QEC113-ND and the IC PhotoTrans QSC112-ND also became obsolete.
I have chosen some Dig-Key Part No’s as replacement, and added a new circuit.
============================================== Dig Key: http://www.digkey.com Part No. Description QRB1114-ND SENSR OPTO TRANS 3.81MM REFL PCB Obsolete QEC113-ND LED IR EMITTING GAAS 940NM 3MM Obsolete QSC112-ND IC PHOTOTRANS IR 880NM BLACK 3MM Obsolete Replace the Obsolete parts with: 754-1600-ND EMITTER IR 3MM 940NM CLEAR (50 ma) $1.87 per10 160-1030-ND PHOTOTRAN NPN 3MM IR DARK (940NM) $2.70 per10 A364B-4-ND HEATSHRINK 3/64 IN X 4FT BLACK $0.92 per 4 Ft. Q2F332B-ND HEATSHRNK POLY 3/32" BLK 4' $0.51 per 4 Ft (Request To Digi-Key: “Please cut Tubes into 8 pieces, about 6” long.) MPSA27GOS-ND TRANS NPN DARL BIPO 60V TO $2.88 per 10 100KQBK-ND RES 100K OHM 1/4W 5% AXIAL $0.59 per 10 680QBK-ND RES 680 OHM 1/4W 5% AXIAL $1.18 per 20 270H-ND RES 270 OHM 1/2W 5% AXIAL $0.83 per 10 1080-1122-ND LED SS HI EFF RED DIFFUSED 3MM $2.84 per 10 1N4148DICT-ND DIODE SWITCHING 75V 0.15A DO35 $1.06 per 10 If your train room has incandescent lighting use Circuit 1. If it has florescent lighting (makes very little IR light) use Circuit 2. For the IR Photo Transistor, cover it with 3/64” heat shrink tubing, shrink the tubing, and cut the tubing at the face so that there is about a 1/16” dia. hole at the top. Putting two 100 K resistors in series, increases the sensitivity. In parallel, it reduces the sensitivity to any light. Note: The ½ Box Car pictures, are Logic Rail Technologies: http://logicrailtech.com/od-1.htm Bob Frey
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Dig Key: http://www.digkey.com
If your train room has incandescent lighting use Circuit 1. If it has florescent lighting (makes very little IR light) use Circuit 2.
For the IR Photo Transistor, cover it with 3/64” heat shrink tubing, shrink the tubing, and cut the tubing at the face so that there is about a 1/16” dia. hole at the top. Putting two 100 K resistors in series, increases the sensitivity. In parallel, it reduces the sensitivity to any light.
Note: The ½ Box Car pictures, are Logic Rail Technologies: http://logicrailtech.com/od-1.htm