Hello
I successfully created a pulse signal with the 555 IC that makes a led blink. I then added an inverter IC to make another led blink in an opposite way.the whole thing runs of a 3v battery. However after wiring the vcc and ground of the ic the blinking got noticably slower and when wiring the output of the 555 to the input pin of an inverter the blinking stopped ..
I wonder what is going on ...
Hi @grossdan,
It is is tricky to know what is happening, but a couple of thoughts:
- Make sure you have decoupling capacitors for both the 555 and the 04 chips, connected directly from the VCC to the Ground pins of each chip with short leads, to act like a 'private power reservoir' for each chip..
- The original 555 design has been widely copied with different versions having slightly different specifications - the original used biploar technology, and was only specified to run in voltage range of 4.5V to 16, although Wikipedia ( https://en.wikipedia.org/wiki/555_timer_IC) suggests many of these chips worked down to about 3V. From memory, the oscillation frequency is supposed to be independent of voltage, but obviously there are limits. The latter CMOS version is reported as being more flexible, specified down to 2V. However, as this chip has been so widely coped and cloned, it is hard to be sure of the exact specification for your particular chip has. I suggest you try it with an extra battery cell, to see if it is happier with 4.5V supply. If that helps, a different 555 may be more successful, but if it doesn't fix the problem, look elsewhere for a solution ....
- plus of course, check for a wiring error .. e.g. with battery disconnected, measure resistance from negative battery lead to each of the component pins (chips, resistors and capacitors) connected to 'gnd', in case one is missing. Then repeat the same for the +3V lead to the 'Vcc' pins.
Good luck with your troubleshooting. Best wishes, Dave
It may be that your additional connections are changing the capacitance in such a way as to affect the 555 (a schematic would help). You could isolate the 555 from the led load by using a transistor as a switch driven by the 555. Just a thought.
I edit my posts to fix typos, correct grammar, or improve clarity. On-screen keyboards are evil.
Hi @grossdan,
Having just read @binaryrhyme 's suggestion, it occurred to me that it the 555 output is buffered, so should not need a separate buffer for a modest load like an inverter. So maybe you have accidentally connected your inverter input to one of the 555's timing control pins instead of the output pin?
@davee thank you.
I did do some wrong wiring, but in the end the output of the 555 is driving a led via a resistor. So, I wired the output of the 555 to the input of the inverter also.
But, was it weird is that just by powering the inverter chip -- with the battery connected to its Vcc and ground to ground, the blinking gets slower -- without yet connecting the 555 output to the inverter input.
I think the clue, as @BinaryRhyme suggests, and indicated by the reduced blinking rate -- must be related to capacitance -- somehow -- and reduction in blinking spead, must mean more capacitance, given how the 555 in astable mode is setup to work-- so somehow the inverter has done that.
I am now thinking that i placed the inverter very close to the 555 chip on the breadboard -- i will put each on a separate breadboard and see what happens ... and perhaps a seperate power suppy also (eventually)
Looks like the chip was defect .. changed to a different chip and it works now.
I guess those chips one gets from Ali express may or may not work