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  1. Xeno Xenox

    Clean square waves using a 555 timer?

    The picture I shared appears to be the same picture that you cropped and painted over. Although it could obviously be a Chinese counterfeit, the unmodified logo looks similar to the TI logo. It certainly isn't symmetric like your paint-over. It's shaped roughly like the state of Texas, albeit...
  2. Xeno Xenox

    Clean square waves using a 555 timer?

    The labeling matches TI. Is it possible it's just a worn/distorted TI logo?
  3. Xeno Xenox

    Clean square waves using a 555 timer?

    @dorke: Will you please post a photo of the chip and its logo? I may be able to track it down.
  4. Xeno Xenox

    Clean square waves using a 555 timer?

    @TedA: Thank you for your thoughtful and highly informative response! I agree that the earliest sharp spike I saw well above Vcc was inductance affecting Vcc. I've verified this by removing and experimenting with various bypass capacitors. Your theory of transistor storage delay being the...
  5. Xeno Xenox

    Clean square waves using a 555 timer?

    Interesting... All of the chips I've tested have been labeled as Texas Instruments NE555 chips. Do you know what variation of 555 you used?
  6. Xeno Xenox

    Clean square waves using a 555 timer?

    @CDRIVE: If you build my circuit using that SPICE macro, can you recreate the voltage hump at the beginning of the high phase?
  7. Xeno Xenox

    Clean square waves using a 555 timer?

    @chopnhack @hevans1944: I misspoke. It was this same 20 piece set of caps I purchased on Amazon for $13.37 -- not a 10 piece set.
  8. Xeno Xenox

    Clean square waves using a 555 timer?

    @dorke: I purchased 10 tantalum 10uF caps through Amazon for $13.37. They'll arrive Thursday. Do you know of a less expensive source? When I get some time, I'll try your three tests. Out of curiosity, is no one else able to build this circuit? :)
  9. Xeno Xenox

    Clean square waves using a 555 timer?

    Here's the board I'm thinking of using:
  10. Xeno Xenox

    Clean square waves using a 555 timer?

    @dorke, @hevans1944, et al. I sincerely appreciate that you are now also interested in finding the theoretical cause of the 555's behavior. Considering a dead-bug build, I don't have any solid copper PCB board lying around. Would it suffice to solder the circuit onto a prototype board with...
  11. Xeno Xenox

    Clean square waves using a 555 timer?

    @hevans1944 @dorke: What I've learned from all of this is that, while the 555 is a versatile chip, it's also very temperamental. Theory and simulation seem to do a poor job of predicting the real world outcome of 555 circuits, so it's best to build them out and tweak them until you get the...
  12. Xeno Xenox

    Clean square waves using a 555 timer?

    Here's the "working circuit" with no load: And here's the same circuit with the RC load from the "non working circuit": My interpretation is that the added load draws the voltage down below 8V and it gradually recovers to 8V as the capacitor charges and the current demand drops. Do...
  13. Xeno Xenox

    Clean square waves using a 555 timer?

    The scope is generating a 3V peak-to-peak signal on its probe compensation output and to the best of my knowledge, that output is only designed for probe compensation. Connecting it to an active circuit driven by a 9V supply seems like a bad idea. Instead, I used my function generator (a...
  14. Xeno Xenox

    Clean square waves using a 555 timer?

    I used 555 timers from two batches. The first batch I've had in my collection for years and the second batch I ordered through Amazon (from China) a month or so ago. All of them have exhibited the same behavior.
  15. Xeno Xenox

    Clean square waves using a 555 timer?

    @CDRIVE: I'm not sure what's going on with the images. It is affecting posts #44 and #49. The images sometimes show up and other times don't. It appears to be an issue with the Electronics Point forum itself. You can see the scope traces for the working circuit in post #27 of this thread...
  16. Xeno Xenox

    Clean square waves using a 555 timer?

    1. I understand your theory behind point 1, but it doesn't have much impact in practice. I replaced the 1K with a 33K and see no change in the <8V output level. I then tried 330K and see a very slight rise to around 8V exactly. I pushed it even further to 33M and the output still doesn't...
  17. Xeno Xenox

    Clean square waves using a 555 timer?

    I successfully got the circuit to generate a 50% duty cycle by replacing R1 (in the first schematic in this thread) with a variable resistor and then tuning it. R1 acts as a pull-up resistor to help the capacitor charge faster and discharge slower. By making it tunable, I can tweak the duty...
  18. Xeno Xenox

    Clean square waves using a 555 timer?

    Here's the signal with the probe connected directly to the calibration terminal: Here's the signal with the probe connected through the blue wire to the calibration terminal: I couldn't find a meaningful difference at any time scale. And here it is connected through the blue wire, through...
  19. Xeno Xenox

    Clean square waves using a 555 timer?

    I hope you'll forgive me, but I can't tell if you support the proposition that solderless breadboards are useless for anything but DC or support it. Am I the one beating a dead horse? :)
  20. Xeno Xenox

    Clean square waves using a 555 timer?

    @dorke: Do you have a theory as to how a transient on Vcc, the control voltage pin or elsewhere during the rising slope could cause the 555 to stabilize at less than 8V (when Vcc is 9V) during the high phase of the square wave? The 8V out of 9V is the problem that's preventing the circuit from...
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