Touch circuit sound, led. 555 timer

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eTech said:
Disconnect X8 from U2, P3 so it is isolated from the rest of the circuit. We'll try to test maually by touching the junction of X8/R7 to ground.
Click to expand...
X8 from U2? I'll need a little more direction
Isolate P3?
All I got right is x8/r7 to ground
 
ThomsCircuit said:
X8 from U2? I'll need a little more direction
Isolate P3?
All I got right is x8/r7 to ground
Click to expand...

+5
|
R7
|
+---- <-----2. connect this junction to ground
|
X8
| <----- 1. lift X8 lead out of breadboard so its not connected to anything
|
555 out, pin 3 (U2)
 
I applied power, waited 1 min, pressed button once. Watched all leds come on (green & orange) after 16 seconds it performed as before. Orange led went out, green stayed on, relay remains engaged. With probe to ground and the other on pin10 of 4013 the voltage remains low 0.022v
 

Then there is something wrong with this part of the circuit. If you connect a wire from ground to the junction of R7/X8, 4013 P10 should change from low-to-high as long as the ground wire is connected. If you disconnect the ground wire, the voltage should change from high-to-low.

This is the only PNP transistor used. Maybe connections swapped? Can you read the manufacture name on the body? Then we can check.
 
Last edited:
I got those from ebay.
I tested them. They are PNP transistors but my test doesn't show if they actually work.

I can get a different batch from tayda.
B327 40TA
B327 25
B327 25TA

I'll get whichever you suggest. I would do the B327 25
 
I'm hoping I performed the test correctly. I did another with this slight change.
No buttons pressed. Tested pin10 voltage 0.022
Removed the ground pin from junction R7/X8 and tested pin10 voltage unchanged. Did you look at my photo for the new test setup? I don't understand why X8 is still in the breadboard with one leg removed.
 

I left X8 there to save time, but for this test it can be removed from the breadboard if you want. It won't effect the results either way.
The problem with unbranded parts is you don't really know what your getting. I'm in the US and always get parts from Mouser.com.
Sometimes the pin assignments are different, but with a branded part you can verify with the datasheet.

Before we decide the transistor is bad, leave the ground wire installed and check the voltages at each E,B,C pin of Q1.
report back.
 
Odd?
With the button pressed. Relay engaged. If I touch the collector, or base pin, or pin10 with my screwdriver the relay disengaged, leds change back to standby mode.
 
Last edited:
ThomsCircuit said:
Odd?
With the button pressed. Relay engaged. If I touch the collector, or base pin, or pin10 with my screwdriver the relay disengaged, leds change back to standby mode.
Click to expand...

Might be noise getting into pin 10 causing a reset.

Check the value of R10 with your ohm meter....its supposed to be 10K.
(remove it and measure)
 
OK...then I think we've tested all we can and can conclude Q1 is bad.

I'm using a BC327-40. but a 2n3906 or 2N4403 will work also.
 
Notice that the BC327 has pin out reversed from most - reading with the flat side to you and pins down -
Collector, Base, Emitter.
 
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