Yes I would say that they were not very compatible. Look at the peak wavelength. For the emitter it is about 950nm and for the detector it is 800nm. The detector only has a 40% sensitivity at the wavelength your emitter is putting out.
What arrangement do you have? Is the detector's resistor in the emitter (of the detector) or the collector? It needs to be in the collector with the emitter grounded. The illuminance versus collector current suggests you should be using at least a 50K resistor if not a 500K one.
Thank you. Yes, I contacted the supplier of the photo transistor and the emitter today. He said, even though the peak wavelength and the spectral sensitivity is not in the exact same spec, that doesn't mean the photo transistor never responds to that IR emitter. He said, I need to check on the circuit because the photo transistor must be responeded to IR within 10mm range.
On the photo transistor side, I've been keep testing it with a razor pointer as the IR emitter doesn't have any effect on the photo transistor.
I use a razor pointer like this one.
I tested with so many resistance value on thephoto transistor, but 40kohm was the maximum resistance(at 9v) for the photo transistor. Otherwise, the photo transistor never responds even to the razor pointer if I put more than 40kohm.
This is the circuit.
On the IR emitter side, I put 60ohm which is the minimum resistance value(at 5V) for the emitter.
This is the circuit.
When I put resister in the collector with the emitter grounded, the motor just spins regardless of any detection of beam.
Better still use the detector as part of a darlington pair to get the gain up like in my sneak thief project.
Do you have the specification of your darlington pair? how much is the price? Because I need to use a lot of those IR emitters and detectors.
The Ir emitter and the detector I am using now costs little. so.....for the cost saving....
What exactly have you connected to the photo transistor that isn't responding ? If you're limiting current through a high value resistor, you can only connect a very high impedance detector to it such as a digital voltmeter or an input pin on an arduino.
Make up a circuit like below and put a voltmeter across ground and the test point. Make the LED an ordinary red one since your photo transisitor is more sensitive to that than the IR you have. (Its also obvious if its lighting up). If it working properly, you should have a voltage close to 5v when the LED is off and close to 0 when the LED is on. It will gain you some experience in what you're trying to achieve. See what effect changing the resistors and the alignment of the LED and PT has on the voltage. If you can get it to switch between well above 2V and well below 2V then its suitable to be picked up by a digital pin at the test point.
I connected a DC geared motor in the photo transistor circuit so that the motor could spin when the detector responds.
Thank you for the great schematics for my further experimentation.
I supplied 4.8v to the that circuit and the volt meter shows 4.53v when the LED is off, and shows 4.38v when the LED lights up.
So, I beamed the razor pointer to the photo transistor then, the value is 2mV. When I flash a light(normal flash light), it shows 3.7V.
So, I arranged an IR emitter circuit on the arduino and I brought it to the photo transistor. The volt meter shows 1.4v when I touch the photo transistor with the IR emitter. When i bring back a little bit like 5mm the voltage was 2.5V(when well aligned). I must apart those IR emitter and the photo transistor at least 5mm for my final application.
Anyway, I tried to get an arduino digital pin on the test point you mentioned. The digital pin reading showed "1" when there is no beam of IR emitter. When I touch the photo transistor with the IR emitter, the reading was "0". in between, it showed just "1". So, I changed it to analog read. This is the reading from the serial monitor.
start
932
927
926
923
923
925
928
929
934
937
929
924
917
913
906
897
875
845
765
684
656
586
572
561
550
563
582
601
609
575
426
484
432
397
365
337
286
192
233
177
167
55
9
7
3
2
3
5
4
4
4
4
3
4
5
5
6
4
2
2
1
4
4
5
3
5
7
6
5
6
5
4
6
7
6
6
5
6
6
5
15
80
215
240
184
160
83
75
67
62
29
73
56
15
11
12
11
13
14
13
14
41
48
22
29
18
19
36
31
23
30
31
56
62
72
117
135
138
142
128
147
170
157
176
177
169
163
168
174
199
167
178
175
176
167
167
165
162
168
164
172
161
165
181
202
217
223
229
271
314
369
435
457
495
527
As i bring the IR emitter to the photo transistor, the value decreased significantly. But, it is only decreasing when the IR emitter reach to a point where it almost touches the photo transistor.
) (0.06 is 60mA) In practice thats a minimum for 5 volts, LEDs will usually light up at a small fraction of their maximum forward currrent. Personally I'd start with around 200-500 ohms and feed it directly from the digital pin (forget the transistor). An LED including an IRED should always have a resistor. The less you stress them, the longer they last.
