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  1. CDRIVE

    Clean square waves using a 555 timer?

    Sorry to say no. Moreover I wasn't even able to produce a 50% duty cycle. For some odd reason C is charging nearly 3 times faster than it's discharging. The thread has become long, so to save me time sifting through it please post your most recent schematic so I can reproduce it exactly. RE...
  2. CDRIVE

    Clean square waves using a 555 timer?

    Update: Tina provides 555 models in both Spice and Spice Macros. I swapped out the pure Spice model with a Spice Macro and Vo now follows that load vs. voltage drop graph closely. My apologies to Xeno for drifting off of the overshoot issue! Chris
  3. CDRIVE

    Clean square waves using a 555 timer?

    Hop, the Load / No Load was the only issue I was addressing. Not the fact that the 555 can't swing to the Vcc regardless of source load. My sarcasm in that post seems to still be lost in the Twilight Zone so before I become exasperated I'll let it go. That said this graph clearly shows ~ 1V...
  4. CDRIVE

    Clean square waves using a 555 timer?

    I must have spent at least 45 minutes struggling over how, exactly, I was going to reply to this. This is because your reply would only make sense if I just fell off the bed of a truck and was absolutely clueless about the relationships between R C in series or parallel circuits. Nor am I...
  5. CDRIVE

    Clean square waves using a 555 timer?

    Dork, I realize that but it doesn't matter if that cap was the size of a 50 Gal drum. It still has a 1KΩ in series with it; which will limit the peak current to 8mA. Chris
  6. CDRIVE

    Clean square waves using a 555 timer?

    This is now a moot point but I doubt that Adam meant for his suggestion to be performed with the circuit powered. Even if he did it's highly unlikely to damage the scope's cal output because the cal's output impedance will be far lower than the value of R2. Thus the cal output will never let the...
  7. CDRIVE

    Clean square waves using a 555 timer?

    Yes, you ancient, decrepit, old fart but I'll drink to that! :p BTW, I love Adam's last suggestion regarding the scope cal output tied through the breadboard. It may only be yet another straw but no point in not grabbing at them now!;) Xeno Xenox, has this been asked yet? Where did you get...
  8. CDRIVE

    Clean square waves using a 555 timer?

    For some unknown reason your images aren't visible to me. That said your tests in this quote has me really scratching my head. Possibly because I've lost track of things. Do I understand correctly that the 555 + Diode configuration doesn't reproduce the same overshoot and 8V (level off) issue...
  9. CDRIVE

    Clean square waves using a 555 timer?

    I'm saying that they're a wonderful invention for rapid prototyping and general experimentation but they're limitations (when used in the realm of fast rise and fall times) should always be factored in when analyzing a circuit. If you ever get the itch to play in the RF sandbox the solderless...
  10. CDRIVE

    Clean square waves using a 555 timer?

    Talk about shoveling sh!t against the tide! When dealing with anything other than DC I've lost count of how many times the pitfalls of solderless breadboards, lead length, ground planes, decoupling, etc have been reiterated throughout this thread. I think this severely beaten horse died...
  11. CDRIVE

    Clean square waves using a 555 timer?

    I said "Always use x10 whenever possible." It's not an ambiguous statement. In his case there's more than enough output voltage available, so he has absolutely no reason to use x1. A further note on this should include that a fundamental factor of ALL instrumentation is that it should appear as...
  12. CDRIVE

    Clean square waves using a 555 timer?

    I should have mentioned this before but in response to my probe mode question you replied x1. This is not a good practice. Always use x10 whenever possible. Even though you said that either mode didn't change anything I can guarantee that it will in the near future. Just about the only time...
  13. CDRIVE

    Clean square waves using a 555 timer?

    Maybe I can't see it but I don't see a bypass (decoupling) cap (should be mounted close to pin8) on the Vcc to GND rail. This is always SOP but can only be partially effective when breadboarding on a solderless protoboard. On a related note be careful when hanging large caps on the Vcc rail...
  14. CDRIVE

    Clean square waves using a 555 timer?

    Please post some photos of the circuit with the scope probes included. Also, I'm not familiar with Rigol digital scopes so I don't know if your text readouts convert values based on whether the probe is in x1 or x10 mode. Are you using x1 or x10 mode? Yes, grabbing at straws! Chris
  15. CDRIVE

    Clean square waves using a 555 timer?

    RE overshoot and Vo voltage drop: Have you scoped the Vcc pin? Chris
  16. CDRIVE

    Picaxe/mcp23027 i/o exp interface circuit diagram

    Well, that didn't take long. ;) Westaust MCP23017 To Picaxe Tutorial Enjoy! Chris
  17. CDRIVE

    Picaxe/mcp23027 i/o exp interface circuit diagram

    Dev, I've also been searching through the Picaxe forums and faq links in attempt to find the thread that your archived link points to. I did find the thread but the picaxe member failed to include a link to a tutorial he sights. Instead he posted this.. "Thanks for the westaust55 tutorial on the...
  18. CDRIVE

    Picaxe/mcp23027 i/o exp interface circuit diagram

    Perhaps this may help. It's a complete Picaxe / I2C tutorial. http://www.picaxe.com/docs/axe110_i2c.pdf Chris
  19. CDRIVE

    Picaxe/mcp23027 i/o exp interface circuit diagram

    Hey Dev, I'm a bit late to the party but I gotta say that's some oddball code! The "Pause" function in PicaxeBasic is in milliseconds. The first task that code executes is "Do Nothing" for 8 full seconds! After that the subsequent code contains a bunch more long Pauses, including two 4 second...
  20. CDRIVE

    Why I prefer electronics to plumbing

    Bob, I began laughing just from reading your title. I think we're related! :p Chris
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