Proximity sensor - help for a school project

[ericgibbs]

Yes, R9 is not represented, as it is going to be soldered directly on pins 2/13.

Ok, but you should have told me first..

Did you fix the other error OK.?

EDIT:
Looked at your last layout image, looks OK.

 

[DWBH]

Thank you very much Eric!

 

[ericgibbs]

Thank you very much Eric!

Your'e welcome.

When you have finished the project, I would suggest you post it, others may have a simlar requirement.

 

[DWBH]

Will do!
I'll etch the board and populate it this week, so I'll tell you guys how it goes.

 

[tcmtech]

Neat! A high tech Tennis ball in a string!
Drive in untill the ball touched the windshield. Then stop.

Thats how the old timers did the garage parking asistant in the days before common sense was abolished.

The electronic ones used a D battery instead of the golf ball. It gave a noticeable audio feedback (klunk) when you were there!
Even if the battery went dead It still worked!

 

[ericgibbs]

hi tcm,

I see the project as a school learning project, by doing it, the pupil has learnt and improved his skills on circuit drawing and pcb layout.

He is now going to etch the pcb and assemble the board after which he will test it.

I guess its mostly his own work which has corrected after our checking and he did say from the start it was a school project.

If I'm over reacting say so., perhaps you were just joking.

 

[tcmtech]

Oops my bad, I forgot to put the sarcastic faces at the beginning and end of my post.
I was just poking a little fun at him. no actual harm intended!

His post just reminded me of a person I know that wanted to have a way of not hitting the wall with his pickup every time he parked it. (Big pickup, tight fit)
He said He would pay me $100 if I designed him a reliable sensor system.
I put a golf ball on a string and a wedge shaped wood block on the floor with a paint outline of where it was to be. (tire Blocker)
I didnt get paid but he does not ask me for help anymore either! Thats worth the golf ball and wood block right there!

All honsty This poster does have great idea and a well thought out aproch!
Nice work!
Sorry if my humor did not transfer properly on the first post.

 

[ericgibbs]

hi tcm.

As you know we get so many OP's saying I want the circuit and program for a project "I am going to design",
its nice from time to time to get someone who has put some effort into doing it himself and given a good presentation.

What I liked about him, was that he stuck with it until he got it right.

Not a 'one post wonder'.

 

[tcmtech]

Very true! I have been watching this thead for a little while. I do have to admit I may have to pirate this for my own use!
(Once he has it debugged and fully functioning of course!)
The newbies want our knowledge to get good grades. Is it okay if we take theirs once in a while?

DWBH your a good example to all the newbies with homework questions!

 

[DWBH]

I've had some troubles with the sensor.
When I power it, the piezo starts bipping non-stop, no matter where the leds are. In fact, even if the two leds are disconnected, it still bips.
- Both LEDs are working fine (I tested them out of the circuit with a DMM)
- D3 shows continuity on both ways - a diode shouldn't do this!
- C1 shows continuity on its leads.
- C5 shows continuity on its leads.
- C6 shows continuity on its leads.
- Not really sure about C4, but I think this one is ok.

Do you have any clues.
The buzzer I'm using is rated at 6v, although the circuit is optimized for 12v. However, I power it with 6v and it works the same way - a constant, irritating beep.
Do you have any clue on what is going on here? Can you help me out?

Here's the schem:
**broken link removed**

 

[colin55]

Firstly, you have presented a circuit diagram with no component values.
Secondly, if you are measuring components "in-circit" you have absolutley no idea about electronics.
You have taken on a circuit that is far too complex for your ability.

 

[ericgibbs]

I've had some troubles with the sensor.
When I power it, the piezo starts bipping non-stop, no matter where the leds are. In fact, even if the two leds are disconnected, it still bips.
- Both LEDs are working fine (I tested them out of the circuit with a DMM)
- D3 shows continuity on both ways - a diode shouldn't do this!
- C1 shows continuity on its leads.
- C5 shows continuity on its leads.
- C6 shows continuity on its leads.
- Not really sure about C4, but I think this one is ok.

Do you have any clues.
The buzzer I'm using is rated at 6v, although the circuit is optimized for 12v. However, I power it with 6v and it works the same way - a constant, irritating beep.
Do you have any clue on what is going on here? Can you help me out?

Hi DW,
Look at the attached image, measure and post the voltages at the points A,B,...E , and +Vs.

I'll let you know what to do after I get your readings.

 

[DWBH]

Will do, probably later this afternoon. In the meantime, I've been 'poking around' with the ICs and I think the problem is near IC4. Without IC1 and IC2 (only IC3 socketed) I get the same bip.
Thanks Eric.

 

[DWBH]

+Vs - 9,6v
A - 0,48v
B - 0
C - 0
D - 0
E - 0,05v

Though I have to add that these were taken without IC1 nor D1/D2 (IR Led/receiver).
I'll take note of those voltages with IC1+D1/D2 later today.

 

[ericgibbs]

+Vs - 9,6v
A - 0,48v
B - 0
C - 0
D - 0
E - 0,05v

Though I have to add that these were taken without IC1 nor D1/D2 (IR Led/receiver).
I'll take note of those voltages with IC1+D1/D2 later today.

hi DW,
The +Vs should be at +12V.
The A is OK.
The B,C,D should be at 0V for no signal to the D2 IR detector.
Also the E voltage is OK.

If the wiring on IC4 is correct then pin 3 should be close to 0V and the buzzer should not operate.

Are you using TTL 555's or CMOS 555's, recheck pin3. Let me know.

I suspect pin3 is about 1V or 2V, this would cause the bleeper to beep from time to time especially its a lower voltage bleeper.

 

[DWBH]

IC4 (NE555)
1 - 0v
2 - 0,05v
3 - 8,2v
4 - 9,52v
5 - 6,3v
6 - 0,05v
7 - 0,05v
8 - 9,52v

 

[ericgibbs]

IC4 (NE555)
1 - 0v
2 - 0,05v
3 - 8,2v
4 - 9,52v
5 - 6,3v
6 - 0,05v
7 - 0,05v
8 - 9,52v

hi,
As pin 3 is high at +8V the beeper will sound, does it make a continous sound.?

Have you tried holding the 555 with the emitter diode close to the detector diode.?

Also as I said earlier the circuit is designed for 12V operation, not 9,52V.

The circuit works OK in simulation, the only problem with the design is that the beeper 555 is not RESET at power up and so it requires that the detector diode 'see's the emitter so that it can time out, then its ready for normal operation.

 

[DWBH]

I already tried it at 12v today at school, but with no luck.
It does make a continuous, non-stop bip. Yes, I've tried with both LEDs, close together.

 

[ericgibbs]

I already tried it at 12v today at school, but with no luck.
It does make a continuous, non-stop bip. Yes, I've tried with both LEDs, close together.

hi,
Post a photo of the front and back of the pcb, showing the components.

When you say a 'continuous, non-stop bip', is the buzzer going on and off, if so what is the approx rate.?

Do you have access to a scope.?

 

[DWBH]

Non, the buzzer is not going on and off. It's going on, always. It never stops.
Unfortunately I do not have access to a scope.

- D3 shows continuity on both ways - a diode shouldn't do this!
- C1 shows continuity on its leads.
- C5 shows continuity on its leads.
- C6 shows continuity on its leads.
- Not really sure about C4, but I think this one is ok.

Isn't D3 working badly?