And now a full schematic of the 555 timer oscillator with single step and free run option.
By Julian
Youtuber, shed dweller, solar charge controller aficionado
Good morning all…
Youtuber, shed dweller, solar charge controller aficionado
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The strange behaviour is a ground loop, there are several amps circulating when the switch closes. That reverses or lowers the voltage on the other side of the breadboard.
The strange behaviour is a ground loop, there are several amps circulating when the switch closes.
I suspect that you might gain some insight into your unanswered questions in this video by connecting your scope to the Vcc and ground pins of the chip, triggering off of the output waveform as you did before…
I suspect the knee on the positive pulse a simpler explanation. The output of the 555 timer is a totem pole output. The output goes high into the load which has some natural capacitance which can be reflected back through P-N junctions to the input of the load multiplying that capacitance. The output rises to the V-CE of the output transistor, then the much lower base current I-BE charges the 'capacitance' of the load the rest of the way to source voltage.
Hey can you make a high voltage capacitor charger using IC 555?
I may be wrong but it could be the capacitor is not fully discharging. That might explain the fast rise to about 80% and the slow rise to vcc is the capacitor at full charge.
The curve probably has to do with the internal powersupply of the 555. Seems to me that the SR Flip Flop might not get the full voltage right away. Thats the only possible explanation. Ive never put one under an electro microscope,could be as easy as thin wires or induction which provide some resistance and thus not a sharp flank.
theres a far simpler way for a continuous free run oscillator, link pins 2 and 6, as above but do not use pin 7, capacitor from this point to ground, resistor from this point to output…. used this circuit loads of times…. as for adapting it for single shot, never yet tried…
Is there a way to implement this with a 555 so that it has an even duty cycle through the whole frequency range? I only have a 10k pot so I had to use a 10uf capacitor to get a human-perceivable speed. The duty cycle is around 40% at the lowest frequency and 88% at the highest. The 88% duty cycle means that even if the clock period is, say, 32KHz, the time it spends turning off and back on again is equivalent to something on the order of 600 KHz. Do you think i'd have better results with a larger pot and smaller cap?
The brilliant Ben Eater just recommended you in his latest 8-bit cpu video
Hi julian is it possible to construct with an accelerometer a circuit for a car breaking light to fast flash, when you heavy break?
If the pot is turned all the way to Vcc and the discharge transistor turns on you are shorting the power rails. You should put a fixed resistor between the pot and Vcc. The parallel resistor will change a linear pot in to a pseudo log one.
Thanks for taking the time to make an informative video in to this useful chip. And to the people who say it is wrong for a clock, how come it is not obsolete.
I think the ESR of the 1uf is sagging the power supply when you have no 1k resistor and the discharge is doing the same thing on the other part of the cycle. To prove this you would need to scope the +ve and -ve of the 555 with your scope. I think it would be important to connect the ground of the scope directly to pin 1 and probe to pin 8 directly so the breadboard is not included in the equation. Another thing, the led has capacitance which can show up on the output. Disconnect the led to prove that.
Tantalums can exhibit weird behavior, might be worth doing the 'scope test again but pull the 555 out, and see if the shelf thingy happens without the chip in place.
Enjoyed the video, didn't enjoy the fact youtube played a Conservative Party political broadcast until I managed to get to the skip link. Surely this can't be right
Just curious as to why a 555 was used. There is a simple two transistor astable that can be messed with to do the exact same job as was used decades ago for some homebrew 6502 and Z80 simple computers in the early 80's (with a toggle switch for single stepping). Just to reduce component count or some other reason?