Circuit doesnt work with IR-Diode

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-skunk-
 
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Circuit doesnt work with IR-Diode

Post by -skunk- »

Hallo,

ive just build this nice thing on a breadboard. ive only connected LED5 and one transistor on PB1. testing the circuit with a blue LED on the collector of Q3, it works. LED5 blinks after each code and after all, it blinks three times. when i connect an IR-led to Q3, nothing happenes. resetting the atmel, LED5 blinks one time and nothing more happenes. the IR-led itself works fine, ive tested it with a cam. (ive also tested different IR-LEDs).

id be very glad if you can help me because i dont know whats going on :)

jwsk
 
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Post by jwsk »

did u also burn the fuses?

i had some strange effects before burning the fuses!

avrdude -p attiny85 -P usb -c usbtiny -B 250 -u -U lfuse:w:0xfd:m -U hfuse:w:0xdf:m

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-skunk-
 
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Post by -skunk- »

the makefile ive used contains these fuses:

$(AVRDUDE) $(AVRDUDE_FLAGS) -B 250 -u -U lfuse:w:0xfd:m -U hfuse:w:0xde:m

edit:

i think thats not the problem because it works fine with a blue led.
(please dont tell me that i doesnt see the ir-leds :))

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opossum
 
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Post by opossum »

Batteries are too weak. Try fresh 2xAA or 3xAA.

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-skunk-
 
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Post by -skunk- »

im using a switching power supply and ive tested the specific voltage range 2,7-5,5V.
i think a higher voltage isnt the solution because the ir-led works at 1,3V, the blue one at 3,xx V.

another question is, where do i use the 47Ohm resistors that are listed in the parts list? ;)


edit:
it works with 2 IR-leds and a 120Ohm resistor in series...
due to this, the range is pretty small...

Probedude
 
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Post by Probedude »

-skunk- wrote:im using a switching power supply and ive tested the specific voltage range 2,7-5,5V.
i think a higher voltage isnt the solution because the ir-led works at 1,3V, the blue one at 3,xx V.

another question is, where do i use the 47Ohm resistors that are listed in the parts list? ;)


edit:
it works with 2 IR-leds and a 120Ohm resistor in series...
due to this, the range is pretty small...
The 47 ohm resistors are in series with the base lead of the NPN transistors driving the IR leds. There is no resistor in series with the IR LED itself. The schematic shows how it is all wired up.

Try your circuit out using a battery as your power supply. Your switching power supply may be too noisy or have poor transient response to be able to keep the atmel powered up when driving the IR leds.

Dave

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-skunk-
 
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Post by -skunk- »

well ive also used batteries to test it.
theres the same problem as seen before.

furthermore im using 120ohm resistors between the atmel and the base of the transistor (as shown in the schematic).

im gonna try a larger capacitor later...

Probedude
 
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Post by Probedude »

-skunk- wrote:well ive also used batteries to test it.
theres the same problem as seen before.

furthermore im using 120ohm resistors between the atmel and the base of the transistor (as shown in the schematic).

im gonna try a larger capacitor later...
But did you use fresh batteries? Use 3 fresh batteries and see if your situation changes. Also see about running a separate wire from your battery + to the Atmel Vcc pin (will clean up the power supply). Don't tie the Vcc pin on the atmel into your breadboard's power bus.

Ooops, I forgot the schematic is incorrect. The resistors shipped with the product are 47 ohm vs the 120 in the schematic. Don't know why that error keeps being reproduced (it's in the 1.0 and 1.1 schematic as 120).

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-skunk-
 
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Post by -skunk- »

using a 1500µF capacitor and changing the resistors from 120 to 68 Ohm it works fine. no need for other changes...

Probedude
 
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Post by Probedude »

-skunk- wrote:using a 1500µF capacitor and changing the resistors from 120 to 68 Ohm it works fine. no need for other changes...
Congrats! Your find identifies what your problem was to begin with - a problem with the power going to the Atmel. Adding the cap stiffened the supply to the Atmel (kept the Vcc up when the IR diode was pulling current).
Somewhere I posted plots showing the current going into the IR diodes for a V1.0 board, ~ 300mA per diode. With a V1.1 style drive circuit it was ~600mA per diode.

What is the lead length from your battery/power supply to your breadboard?

Reducing the resistance from 120 to 68 did nothing to fix your problem.

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-skunk-
 
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Post by -skunk- »

well...connecting Vcc straight to + doenst work at all.

the 68 Ohm resistor causes sth about saturation or sth like that...right? doenst matter at all...

im going to solder that instead of using a breadboard...gonna tell you the result.


thanks for your help!

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