Beginner, infrared proximity detector working wrong way around

MrChips

Joined Oct 2, 2009
23,290
Rather than speculate how the unit purchased was intended to operate, why not design and modify the unit the way you want it to work.

1) Establish which is the emitter and which is the sensor.
2) Select R1, R2, and trim RV1 for desired sensitivity.
3) Accept the logic output as given and design output driver transistor for desired operation.
 

jpanhalt

Joined Jan 18, 2008
11,088
There is no need to make any electrical modifications, except adjust R3, to get the circuit to do what the TS seems to want. All that needs to be done is proper control of the IR light.
 

djsfantasi

Joined Apr 11, 2010
7,641
Rather than speculate how the unit purchased was intended to operate, why not design and modify the unit the way you want it to work.

1) Establish which is the emitter and which is the sensor.
2) Select R1, R2, and trim RV1 for desired sensitivity.
3) Accept the logic output as given and design output driver transistor for desired operation.
Sometimes we forget what the initial problem was. Especially when the real issue is not an electronic one.

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.
The TS was trying to build a simple kit to share the experience with his son. I think “designing an output transistor” driver may not address his problem. Nor may it be within his skill set. Not picking on you MrChips Many if ys, myself included, have fallen into this trap.

@Audioguru again nailed it in post #40. Post #40! We took too long to get there.
 

LesJones

Joined Jan 8, 2017
3,144
I had not realisesd that a link had been posted to the ebay page for the device and had not come to a conclusion what the optical setup was. (Slotted opto, beam break with separate emitter and detector or reflective sensor.) It was only today that I looked at the schematic enough to work out how it was designed to work. Even after the link to the information was mentioned today I did not read all the information as it was difficult to read as I had to scroll from side to side. After the last few posts I went back to it and did a copy and paste into notepad which made it much easier to read. ( I have attached these text files.) I think the TS will have learned more by it not working and following this thread than if it had worked straight away. (If it had worked he would have just got more practice at soldering.)

Les.
 

Attachments

MrChips

Joined Oct 2, 2009
23,290
The TS was trying to build a simple kit to share the experience with his son. I think “designing an output transistor” driver may not address his problem. Nor may it be within his skill set. Not picking on you MrChips Many if ys, myself included, have fallen into this trap.
I fully appreciate that. It is up to the TS to state what he understands and what he does not understand. We are here to provide the required guidance when asked.
 

Thread Starter

notquitethere

Joined Mar 23, 2020
14
Here it is with a pen lid over the receiver, and it's acting as initially expected.

What's odder, though, is it that acts the same WITHOUT the pen lid this evening. It is pretty overcast today, so maybe the external light source theory also has legs?

I can't see any IR when looking at it through the phone camera, and I can't find the standalone digital camera yet to try that.

I did see the mention of "tube" in the original listing, but I admit I discounted it as a translation artefact.

My skillset is definitely limited to soldering-it-together-as-told rather than design at the moment. I've gone through a lot of the Lessons in Electric Circuits textbook but I got rather stuck trying to understand some of the amplifiers and decided to try some practical for a bit instead. You've all been very helpful but may have opened yourselves up to more numpty questions in the future.

I gather I am the TS. Total Simpleton? ;)
 

Attachments

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.)
Hey,
It's Saeed. Dear Sir, I looked at the schematic. We have a wrong thing here. D2 must be IR reciever, but in the parts list it is transmitter one. It's wrong, and you may replace these together. Thanx. Have a good day.
 

Audioguru again

Joined Oct 21, 2019
3,016
I had not realisesd that a link had been posted to the ebay page for the device and had not come to a conclusion what the optical setup was. (Slotted opto, beam break with separate emitter and detector or reflective sensor.)
Les.
The Chinese translation wrongly says, "The hand blocks the IR" instead of saying, "The hand reflects the IR" which the opposite.
 

MisterBill2

Joined Jan 23, 2018
8,502
Hey,
It's Saeed. Dear Sir, I looked at the schematic. We have a wrong thing here. D2 must be IR reciever, but in the parts list it is transmitter one. It's wrong, and you may replace these together. Thanx. Have a good day.
The schematic drawing very clearly shows that D2 is the IR receiver. And the fact that the circuit functions certainly indicates that the correct devices are in the locations for D1 and D2..
The only error is in the description of the device.
 
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