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Hope you had a good sleep.
No, if you are an old hand with the 555 and read the data books, they will not look right- I just like to be different.
All that calculation with the two resistors to get the frquency you want while maintaining a 1:1 mark to space ratio gives me a headache.
Thinking about it I have never used the text book aproach, and I have literally built hundreds of 555 circuits: CMOS version, 556 dual and so on. Even used them as power drivers: the output stage can handle 200mA, in theory anyway.
With my approach you only need one timing resistor, which means that only one pot is required when you need a variable frequency, but not only that, if you use the discharge, open collector output with a 1K pull up, it swings rail to rail and the waveform is a lot cleaner with faster rise and fall edges: ideal for drivinf TTL. Much better than the blood-and-thunder of the Q output.
I allways feel that the 555 missed the boat by not providing an inverting output- would have made the chip much more useful.
It is still a great chip though, just beware of the huge spikes of current that the output stage whips off the supply rail as both transistors in the output sytage crosses over- not a problem with the CMOS version. Because of the current glitches I wouldn't dream of using a bipolar 555 without a 100nF cap strapped across the supply rails.
Looking at the voltages that you posted previously, I now realise that pin 3 has been wrong all along. It should bouce between 0V and 6V with no problems.
Can you check the wiring of pin 3? It should go to the pot only.
I forgot about that 50% duty cycle circuit. I just thought output pin was wierd. I should be sleeping (4:15 AM). I hate the 555. It's stupid in monostable mode. It glitches on power up. I liked the LM3905 **broken link removed** which is obsolete now. The CMOS 555 is a totally different beast than the 555.
I forgot about that 50% duty cycle circuit. I just thought output pin was wierd. I should be sleeping (4:15 AM). I hate the 555. It's stupid in monostable mode. It glitches on power up. I liked the LM3905 **broken link removed** which is obsolete now. The CMOS 555 is a totally different beast than the 555.
Wierd- are you talking about meeee.
I love/hate the 555. What I cant understand is that there are much better timers, but they never caught on. The 555 wasn't supposed to go into production I understand- it was just a design execise at National- I think that is true.
ok i just checked and pin 3 is going directly into pots pins 3&2 then pot pin 1 is going to pins 6 & 2 pin 6 also has + side of 10uf capacitor attached
Can you do this:
(1) Don't turn circuit on.
(2) set the meter to 200K (top left)
(3) measure resistance across RV
(4) Measure the resistance from all the pins on the 555 to the OV supply rail
(5) Measure the resistance from all the pins on the 555 to the 6V supply rail
damn it i asked them for the pot you had in the diagram, ok i dont have a 100k resistor, i may be able to salvage one tho from something else like a power supply or something.
and yes it read 10
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