555 flasher isnt flashing

[KJ6EAD]

I don't believe you are correct about the continuity of your buses. The gap in the red and blue stripes has always indicated a gap in the buses on breadboards I've seen. Try installing jumpers just to humor me and @WHONOES.

 

[messy]

figured out some of the odd voltages - the breadboard rail provides significant resistance apparently....moved the pin connector next to the battery wire and it started getting proper voltage. Still stead on led tho

8.3 on pin 8 supply
5.4 on 7 discharge
5.2 on 6 thres
5 on 4 reset
3.3 on 3 output
5.3 on 2 trigger
3.6 on 1 gnd


when the output is high (which it is) the cap gets charged by current through R1 and R2 (which it is). When the cap reaches 2/3 supply V the output becomes low and discharge pin connected to ground.

the supply is 8.3v so 2/3 is 5.5 - so the threshold is met so now the output should be low which it isnt BUT it seems like the discharge pin IS connected to ground because it showing 5.4 right?

voltage across the cap legs is constant 1.78



ALSO - I took the reset pin and connected it to 0v instead of +V thinking this would set the output to low but ti had no effect on the led at all

 

[messy]

I don't believe you are correct about the continuity of your buses. The gap in the red and blue stripes has always indicated a gap in the buses on breadboards I've seen. Try installing jumpers just to humor me and @WHONOES.

they def are continuous, i have used these boards a bunch, also - the led surely would not light at all if they weren't continuous?

 

[messy]

I don't believe you are correct about the continuity of your buses. The gap in the red and blue stripes has always indicated a gap in the buses on breadboards I've seen. Try installing jumpers just to humor me and @WHONOES.

my sincerest apologies - i looked at the board again and noticed the gap in the very center was wider than the other gaps - when i moved the ground wires over to the battery side it started working!!!!

(shameless excuse - my other breadboard does not appear to have the mid board break)

what i dont understand however is that is the middle line is a gap, how on earth it was getting power earlier when there was no power connection to that side of the gap?!? the only thing on the power rail on that side was one leg of R1

 

[KJ6EAD]

There are various current paths within the 555. Besides the board markings, the low voltages you measured were a clue.

There was a design contest back around 2011 where one entrant used 555s as capacitors and resistors in his circuit so the entire circuit was made of them except the output which was probably LEDs.

 

[Bluejets]

what i dont understand however is that is the middle line is a gap, how on earth it was getting power earlier when there was no power connection to that side of the gap?!? the only thing on the power rail on that side was one leg of R1

I re-checked the values and they are the same however I may be using the multimeter wrong.
When reading the value of the pins im holding the red (V) probe to the chip pin and the black gnd probe to the negative terminal of the battery

That is why you were getting weird readings as your negative to the chip and other components was non-existent to some extent.

Also, as a side note, when using a potentiometer to vary timings, it is a good idea to include a "minimum" value fixed resistor in series with the pot to eliminate zero resistance at one end of travel.