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Mistake when soldering components on PCB

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purifier

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I started making a project. I thought i could directly connect the circuit on a PCB and so started soldering all the items on the PCB. What i did was i drew the exact circuit on the PCB with the soldering lead as the path. Finally what i got was a circuit on the PCB. Now i only had to insert the components at the appropriate places. But to my surpirse... after switching on the supply, there wasn't even a potential drop across the resistor... I thought i made a mistake by joining components using the soldering lead... I didn't use a single wire in the design... Can someone please tell me what mistake i committed?

Here's the circuit i was planning...

https://www.i-hacked.com/content/view/30/57/

Please help...
 

aryajur

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Re: PCB Mistake

If you could post your component layout on the PCB that will be helpful to find the mistake. Also what did you connect to the jacks when you powered up the circuit? And what resistor were you checking the drop on?
 

flatulent

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Re: PCB Mistake

Here are some possible errors to check for in the transmitter.

1. The LEDs are backwards.

2. You are not using a high enough voltage to turn on the transistor.

3. Your BJT is wired in wrong or is defective.
 

purifier

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PCB Mistake

I didn't put anything in the jacks... And i was checking the drop across R1... I guess i didn't quite understand the circuit. What should i connect in the jack? Audio signal? Then what is the wire used to connect the ouput of the audio source to this jacks'a input called? The ciruit needs 9V but i've been giving 8.7V... I'll post the pictures as sson as possible... Please help...
 

IanP

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Re: PCB Mistake

Start testing your circuit in stages.
Stage1(transmitter): shorten Q1 in the transmitter and measure voltage accross R1. In your case it should be ≈6V and that indicates that the 6mA of current is flowing through both diodes. (standard forward voltage for IR diodes is 1.5V, so 2 dides will generate 3V and the remaining 6V has to be on R1).
Now connect 10kΩ resistor between the base of Q1 and (+) of the battery. You should read similar voltages as before.
Stage2(receiver):place 1kΩ resistor in parallel with J2 (this will close the circuit) and shorten phototransistor. This should saturate bot transistors and you should read accross this additional resistor ≈7-7.5V.
Stage 3(transmitter and receiver): with this additional resistor in parallel with J2
place both transmitter and receiver not far away and connect the test 10kΩ resistor between the base of Q1 (transmitter) and (+) of the battery.
Measure voltage accross 1kΩ at J2: you should read again ≈7V when the transmitter transmits or 0V if the transmitter is quiet.
Regards,
IanP
 

purifier

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Re: PCB Mistake

I've taken some pictures of the layout... Please have a look at them...

Transmitter Top View


Transmitter Bottom View


Transmitter Side View


Receiver Top View


Receiver Bottom View


Receiver Side View


Alignment of PhotoTransistor
 

throwaway18

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Re: PCB Mistake

>I didn't put anything in the jacks
The circuits won't work without high impedance headphones plugged in.
You could blow the trasistors in the reciver circuit if you use normal 8ohm headphones.

>What should i connect in the jack?
Read the webpage you linked to.
 

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