Noted, thank you. I might end up trying all this on my own. It might be too much of a TODO list for my six year old to sit through with me: "Yes we're doing it again but THIS time it's slightly different... here, I think"If you replace the PNP transistors with NPN transistors then you must also swap the emitter and collector pins by turning around the transistors.
Please stop posting on IMGUR or at least upload the file to AAC. I can’t see the IMGUR post reliably and the forum discourages off site image posting. If I want to look closely at your picture, IMGUR often screws up and instead of your picture, it displays someone else’.Probably didn't need to use 5 amp wire.
But this doesn't work.
I made another with D2 and R2 swapped and that didn't work either. (Wasn't sure which was around the receiver was supposed to go in R2's position so I tried both.)
I must be doing something wrong, but for it to behave the same way with the pins and components swapped (on different boards; I didn't swap pins AND components on the same board) is mysterious.
Maybe I'll try breadboarding it out next.
Oh, sorry.Please stop posting on IMGUR or at least upload the file to AAC. I can’t see the IMGUR post reliably and the forum discourages off site image posting. If I want to look closely at your picture, IMGUR often screws up and instead of your picture, it displays someone else’.
I'll have to remake one tomorrow because I butchered the original trying to swap components.When I have tried "everything" and nothing works, I take a nap and go back to the start.
First, I don't see anything wrong in theory (see below about PNP transistors) with your original schematic. In the absence of IR, D2 should be off. That makes the non-inverting input (+) higher (in theory) than the inverting (-) input, so output should be high, which should turn off both V1 and V2.
1) Go back to the original and remove D2 temporarily. Are the signals off? If not, what is the voltage on pins 3, 2, and 1. Pin 3 needs to be higher than Pin 2. When that's the case, Pin 1 should be the same or very close to J1. If not adjust R3 until it is. If you can't, go to step 2. Are the signals still on?
The circuit does not show a IR proximity sensor, it shows a reflective "beam break" sensor. So when you put a hand in front you are reflecting the beam and providing a return signal. So the device is working well, but it was misrepresented. It would be called a "retro-reflective beam break sensor.Hi,
I'm very new to electronics stuff, trying to learn it with my young son. We've been soldering together some basic kits from ebay which has gone well so far.
We've just put together an IR proximity detector, though, and it appears to work backwards to the description. It says it should light up and sound the buzzer when waving a hand near it, but it seems to light up and sound all the time but STOP when I put my hand near it.
The schematic:
Partslist:
Circuit board:
Any suggestions for how I try debugging this?
Ebay posting in case it can help; not trying to advertise it:
https://www.ebay.co.uk/itm/10pcs-DI...m-Electronic-Circuit-Suite-DC-5V/352963796317
(Hope this is the right subforum for it. Wasn't sure if here or 'homework' was better.)
I made a little black hood for the receiver using insulating tape, and when I cover it up the signals (peeper + light) are off. When I take it off, the signals are on again.When I have tried "everything" and nothing works, I take a nap and go back to the start.
First, I don't see anything wrong in theory (see below about PNP transistors) with your original schematic. In the absence of IR, D2 should be off. That makes the non-inverting input (+) higher (in theory) than the inverting (-) input, so output should be high, which should turn off both V1 and V2.
1) Go back to the original and remove D2 temporarily. Are the signals off? If not, what is the voltage on pins 3, 2, and 1. Pin 3 needs to be higher than Pin 2. When that's the case, Pin 1 should be the same or very close to J1. If not adjust R3 until it is. If you can't, go to step 2. Are the signals still on? If so,doubletriple check the transistors. Check the numbers on them and lookup the data sheets. They must be PNP and the emitters need to be connected high (as shown). PNP transistors often are viewed to "source" current and NPN "sink" current (others have said the same). In the design you have, the PNP transistors are sinking current.
That is how it is supposed to work. No IR on receiver, signals off. Your main problem seems to be scattered light getting to the receiver from either the emitter and/or from other sources in the room. Try a light tube over the receiver. A plastic straw covered with black tape will work (assuming you can get the straws legally). Leave the end open. Then as you put your hand over it, the reflections should set off the signal.I made a little black hood for the receiver using insulating tape, and when I cover it up the signals (peeper + light) are off. When I take it off, the signals are on again.
Correct. As a comparator, the voltage at pin1 (output) should be either high or low. The higher the voltage at pin 2, the more sensitive the detector will be. Adjust it so the voltage at pin 2 is lower and see the effects. The real test is with the light tube as described. The first time I made an IR proximity sensor, I was amazed at how sensitive it was, because of course, you don't see anything.When I twiddle R3 it seems to have no effect on the voltage at P1, only on the voltage at P2.
The transistors are S9012
I disagree. When configured as discussed in post #36 and elsewhere, it will act as a proximity sensor. That is, unless something reflects the beam into the sensor, its output is low. Putting the IR emitter in close proximity to the detector was a design error, but that is easily fixed. In my application years ago, I put the emitter in front of the detector. In this snippet, the location of the detector behind the filter plastic is circled.Less has it half right. The system is intended to operate as a "Beam Break" sensor. That is the operation described in post #1, with the reflection coming from the hand.
Once again, it IS NOT one of the passive IR motion sensors. Try it with ha sheet of white paper a few inches away and observe that it works as a beam break sensor. Then try it with one of those retro-reflectors like are used on bikes. or better yet, a piece of that reflective tape. The range will be even farther.
The real fault is that it was mis-represented as a proximity sensor instead of a retro-reflective beam breaking sensor.
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