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  1. Old Steve

    External ringer for VOIP phone

    That makes it tricky. It used to be relatively easy with a landline, because the ring voltage direct from the phone line was AC. It sounds like the vendor's external ringer might be the way to go. If it's not loud enough, then you could more easily attach an amp or whatever.
  2. Old Steve

    BPW34 & Rail to Rail OpAmp

    Ben, did you find one yet? Offhand, I can't point you directly to one that'll fit the bill and is also available from Jaycar or Altronics, but if you check out RS Components AU, you can select supply type, (single supply), and output type, (rail-to-rail), in the drop-down boxes on the left of...
  3. Old Steve

    Capacitor Questions

    Farticus, just as an added point, if you want an 'unregulated' 24VDC, using a mains-connected transformer with a secondary voltage of 18VAC would be the most economical way to go. It would provide just over 24VDC after rectification with a suitable reservoir capacitor. (18VAC x 1.414) - 1.2V =...
  4. Old Steve

    Need help on converting 0-5v signal to 0-10v signal

    Yep. If a slight loss of accuracy is acceptable, due to temperature and load variations, the op-amp could be given an 0.6V offset, then an NPN transistor could be added in common-collector mode to follow the voltage. Edit: If a diode was used on the op-amp input to provide the 0.6V offset, the...
  5. Old Steve

    Need help on converting 0-5v signal to 0-10v signal

    Can't you measure the current consumption of the load? Just put a very small-value resistor between the op-amp output and the 'unknown device' input and measure the voltage developed across it.
  6. Old Steve

    Not getting correct voltage from voltage regulator

    Good one, glad it's sorted. Now you can get down to the real fun. Ignore the stuff that's over your head - just follow datasheet guidelines for components and you can't really go wrong. :D
  7. Old Steve

    Not getting correct voltage from voltage regulator

    They're pretty handy, besides as a regulator they make a good reference since they're fairly precise. That's what I was using the LP2950-3.3 for when I got the oscillations the other week - a reference on the input of a comparator. On my DMM, it measured as a higher-than acceptable voltage. I...
  8. Old Steve

    how can I create a positive logic pulse from a steady high input?

    Youre losing me a bit now, (haven't been following all posts), but yes, it should work with the signal from a logic gate. Of course, you could always use a larger value resistor to reduce the load on the previous gate, and then you could use a smaller value capacitor. (I chose those values for a...
  9. Old Steve

    Not getting correct voltage from voltage regulator

    Like I said yesterday, try an LP2950 linear LDO regulator. Again, from the datasheet excerpt that I posted yesterday:- And believe me, from my own experience, it does oscillate.
  10. Old Steve

    how can I create a positive logic pulse from a steady high input?

    Sounds like AK is on the right track. Instead of the AND, diodes would be fine for joining the multiple inputs together. And it definitely wouldn't be worth using a micro unless you planned to use them for other projects in the future. Good toys, though. (And I used to be a bit of a Rush fan...
  11. Old Steve

    how can I create a positive logic pulse from a steady high input?

    Just in case you feel like having a look, here's a link to the PICBasic Pro manual:- http://melabs.com/resources/pbpmanual/
  12. Old Steve

    how can I create a positive logic pulse from a steady high input?

    A micro would definitely be the best/easiest way to implement it, and it would take up the least board space, but the programming is a bit of a learning curve, and the initial cost of a good compiler is reasonably high. Raw microcontrollers themselves, PIC etc, are cheap and a programmer can be...
  13. Old Steve

    how can I create a positive logic pulse from a steady high input?

    Not bad looking speakers. As big as me. (I'm 5'4" tall.) And it sounds like you've been busy. I don't do much discrete logic stuff any more - I cheat and use a microcontroller for most projects. Haven't done anything for some years until the last few weeks, either. I've been busy with my other...
  14. Old Steve

    how can I create a positive logic pulse from a steady high input?

    I forgot to label the gate - it's a non-inverting Schmitt trigger buffer, one buffer from a 74HC7014, for example. If you use this method, tie the inputs of the unused buffers to ground. Leave the outputs of the unused buffers open. In reality, you could probably even omit the buffer, but it's...
  15. Old Steve

    how can I create a positive logic pulse from a steady high input?

    This is one method:-
  16. Old Steve

    Building a soda machine

    Googling "windshield wiper motor operation" will give you a ton of results. https://www.google.com/search?q=windshield+wiper+motor+operation&ie=utf-8&oe=utf-8 There might be a bit more info here too:- https://www.google.com/webhp?hl=en#hl=en&q=volvo+850+headlight+wipers Good luck.
  17. Old Steve

    Not getting correct voltage from voltage regulator

    I've always used caps on the input and output of 78xx series regulators too, but never stopped to analyze the reason. I just blindly do what the datasheet says. (Call me sheep.)
  18. Old Steve

    Light Ignition Circuit?????

    Yeah, first I've seen too. And you're right, that's more or less what it is. Pretty neat. I need to clarify something I said yesterday, too. It fires twice per cycle, of course, and not once as I indicated, so the pulses come at double the mains frequency.
  19. Old Steve

    Mind & Infra Red Controlled Robot Car

    Aside from test circuits, for remote communications, I'll probably use an APC220 module. I have heaps of those just sitting here. They're fast enough for anything I'll do while playing with the idea. (I won't make a car - I'll test the 'mind control' concept for other remote control projects.)...
  20. Old Steve

    LED Circuit not behaving as it should

    No, a crowbar circuit typically shorts across the supply rails, blowing a fuse, to protect a circuit from over-voltage. The diode across a LED just provides an alternate current path when the polarity reverses.
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