DIY Infra-red ? - Page 9 - RC Groups
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Feb 09, 2003, 12:33 PM
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jberg's Avatar

Now it works! :)


today was the second opportunity to test my infrared system. The control is very smooth, just like with a regular radio system.

I have increased the number of LEDs to 20. The peak current per LED is 200mA. They are arranged in 5 parallel groups of 4 LEDs in series, so the overall peak current is 1A, the average current is 80mA.

Now the reliable distance is about 30m. If I place myself in the middle of the longer side of our 45x30m gym then there are some occasional glitches only in the edges on the other side of the gym. The gym is lighted by many fluorescent tubes and a lot of light domes that let daylight in. I have tested the system around noon, so this was already the worst case.

I think I will double the number of LEDs again to be able to fly in the entire gym standing on one short side.

See the gym in the picture (this is the short side). The small bright strips are the fluorescent tubes, the bright squares are the light domes (daylight).
Last edited by jberg; Feb 09, 2003 at 12:45 PM.
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Feb 09, 2003, 12:57 PM
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Jgardner's Avatar

Potential hazard


Great report, encouraging results.

I don't know much about this stuff, but the Aeronutz have talked about the hazards of intense IR. How does your system fit in with thier concerns?

I am clueless on this count, beyond a small bit I have read. I really like the potential for DIY IR, but want to keep it safe.
Last edited by Jgardner; Feb 09, 2003 at 12:59 PM.
Feb 09, 2003, 06:18 PM
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jberg's Avatar

yes, I also think about safety. Up to now I am careful to avoid looking directly into the LEDs and try to tell people that stand nearby not to do so. I thought about putting some super-bright red or green LEDs between the infrared LEDs so that the iris closes when looking at the LEDs and also to know that there is anything coming out of it.


see my testbed model. It is my reanimated Depron Guided Mite (see its "history" here ). I have made a new (now profile) fuselage and a new balsa tail.

- weight 22g
- drive system from ECharger
- GWS 3x2 prop
- homemade actuators

Regards, Jochen
Feb 09, 2003, 06:31 PM
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jberg's Avatar
And this is the receiver, hanging down so that the sensors are visible from all sides. The red LED is a special low-battery detecting type. It lights below 2.3V. I have put a diode (1N4148) in series and an 1k resistor in parallel (to pull a minimum load through the diode), so it will light when the battery goes below 3V.

The receiver's bare PCB with parts was 1g. With all the sockets, the sensors (0.4g each!) and the LED it now weighs 2.5g, still below half of the weight of my previous radio receiver. And the price of the parts is only around US$ 12-15.

Here you see the power part (ESC and battery control LED).
Last edited by jberg; Feb 09, 2003 at 06:33 PM.
Feb 09, 2003, 06:32 PM
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jberg's Avatar
Another picture from the other side. Here you see the charge pump (supplying the IR sensors and the PIC with Andy Birkett's code with 5V which also go to the actuators) and the actuator connection sockets with plugs. These sockets and plugs have a pitch of 1.27mm and weigh vitually nothing (around 60mg per two contacts if I remember it right).

Yes, I confess, I have supported the wires that hold and supply the sensors with a drop of hotmelt glue which is terribly heavy.

The magnet wires that go to the actuators are around 0.2mm in diameter (AWG 36).

Regards, Jochen
Last edited by jberg; Feb 09, 2003 at 06:40 PM.
Feb 10, 2003, 07:53 PM
Registered User
interesing post great pictures and info.
Have you had a chance the try receiver with
one sensor covered? Also have i wonder if the sensor facing towards prop. is effective
due to the signal being chopped by blades
have you noticed any problem with this?
I have my receiver complete and will try
a test friday. I added a amp. to drive a lower resistance coil plus a little larger fet
will try to post picture soon.
Feb 11, 2003, 02:24 PM
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jberg's Avatar

this signal chopping issue is something I didn't think about yet. Maybe it would be better to let the sensors show to the sides. But then the signal will be chopped *and* meet the sides (not the front) nof the sensors when the model is aiming at yourself.

I think in closed rooms the IR signal comes in from all sides due to reflections. And when the model is aiming at you it will not be far away from you for long!

No, I didn't try to fly with one sensor only. Just made some static tests this way.

Regards, Jochen
Feb 11, 2003, 04:45 PM
Was that my 15 minutes?
Andy Birkett's Avatar
I've never know any problems with blades chopping the signal. At the hall we fly in at aeronutz, one sensor will work about 3/4 of the length (so stand in the middle Gordon !!!). Its a single basket ball size court (I think).

The signal comes from reflection in all direction. Try taking your plane upstairs at home and operating is from downstairs, with just a little gap in the intervening doors my (ztron) system still works.

BTW one thing to watch for is decoupling the sensor from the rest of the electronics, this is shown on some data sheets, 4.7F across the sensor, 100R inline with the supply.


Feb 11, 2003, 05:22 PM
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good work by all, but, can someone tell me which peices of the puzzle I need to make a 3CH (esc and two actuator outputs) IR receiver and transmitter.

Feb 12, 2003, 01:04 AM
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Koichi Tanaka's Avatar
When it flew in a big gym, I experienced the influence whose propeller blade interrupts the signal to IR sensor.
The throttle became unstable while flying toward me. However, the flight was only influenced slightly.
One IR sensor was set downward to the airplane.
When flying in the gym of the width of a basketball, there is such no influence. It is thought that it is probably based on reflection.

When two IR sensors were set, such a problem was not generated in a large gym.
Although the sensor of Jochen was set toward back the front, I set towards right and left.

BTW, I think whether a simultaneous flight can be performed using 56.9kHz IR sensor and 38kHz IR sensor. Did someone try the simultaneous flight on IR?

Feb 12, 2003, 08:56 PM
Registered User
This is my first generation IR system
I'm going to increase LED'S in tx. to 50
soon. The rx. has a amp. to drive lower
resistance coils along with FET for motors like the M20.
Feb 12, 2003, 09:06 PM
Registered User
Sorry pictures didn't attach will try again
Feb 12, 2003, 10:03 PM
Registered User
one more time
Feb 13, 2003, 10:43 PM
Registered User
new camera will try again
Feb 13, 2003, 10:49 PM
Registered User
receiver- 2 ch with dc-dc converter,amp for lower
resistance coils and fet

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