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Recent content by mathphobe

  1. mathphobe

    Help with a very simple rc circuit..

    I think making this circuit might be easier than the 555 based one, given I might not need to etch a board. Thanks!
  2. mathphobe

    Help with a very simple rc circuit..

    You should try talking to me in person, its even worse :D I meant the cars directional indicators but the 'pulse extender' answer is still the same so thanks!
  3. mathphobe

    Help with a very simple rc circuit..

    The output from the alarm to the relay 's coil should be 12v 10mA when the alarm is triggered. As that isn't functioning the only other useable outputs are switching on and off in one second periods, I want to spur off that in a way that constantly energises the relay's coil when the alarm is...
  4. mathphobe

    Help with a very simple rc circuit..

    .. for you guys, me.. not so much :( I've installed a car alarm, literally made the final connection only to find out its faulty. There is a fuel cut off relay that isn't receiving a control voltage from the unit. I could replace the alarm but for many reasons it's a ball ache I could do...
  5. mathphobe

    Mosfet gate voltage

    And just when I thought I understood a mosfet I'm reduced to noob again! Obviously I was under the misguided understanding 'saturated' mean fully 'on', apparently not the case. I figured supplying the gate higher voltage would give me better source to drain resistance :( Beginning of paragraph...
  6. mathphobe

    Mosfet gate voltage

    I have been on all of my recent projects, but I'm seeing a fairly large voltage drop through the mosfet. My 4.2 is usually around 3.8 at the drain. With a 1.4mohm rds I should be getting higher Vout of the mosfet fully saturated no?
  7. mathphobe

    Mosfet gate voltage

    Alternating wave form?.. Dam, nothings simple is it :(
  8. mathphobe

    Mosfet gate voltage

    OK BobK, so drawing it isn't going well. I've fell down at making a voltage divider :( pretty sure I'll get there. A brief verbal description; 4.2v (or 8.4v) lipo source. Cap&diode doubler/trippler to lm7805 supplying this part of the circuit. Ds1669 acting as a voltage divider from 0-1v. An...
  9. mathphobe

    Mosfet gate voltage

    Haha, good point. Drawing a circuit on my phone is fairly difficult, doing so only to find that the ideal basis that the mosfet is fully saturated isn't possible makes for a pointless hours work.. I'll attempt it by hand and come back.
  10. mathphobe

    Mosfet gate voltage

    Among several questions I'll likley have while working on a very simple circuit (can you say can of worms :/ ) I want to fully saturate a mosfet from a 4.2v or 8.4v bus source, can I use a voltage trippler capacitor diode arrangement to supply the gate? This would mean a higher gate than...
  11. mathphobe

    Digi pot for pwm board

    I did see page 7 kellys_eye, if I'm honest my minds eye couldn't see it as a circuit though. I'm in every sense a beginner to electronics and very much a visual kinda guy. I'm not great interpreting the purpose of components on schematics dorke, there I see a shmitt trigger, a diode, an rc and...
  12. mathphobe

    Digi pot for pwm board

    Started writing my post earlier but got destracted, hadn't refreshed the page before I finished my question, didn't see your post at all there dorke.. great minds n all that :D Yeah, I saw the dual version but again, no idea how to add buttons or limit the other side to 10k. Anywhere you know...
  13. mathphobe

    Digi pot for pwm board

    ... or am I Sorry, thought I was done but then got thrown a curve ball. The 'choosing correct digipot' pdf says "tap up/down" digi pots can be used with buttons. I've found a 256 tap up/down pot but the data sheet doesn't mention or give a schematic for buttons.. Is the first pdf incorrect...
  14. mathphobe

    Digi pot for pwm board

    I was quite hoping tactile switching or resistive switching would work but its not a problem, for my circuit I'll get a 'contact/closure' interface ic like the ds1869s-100 as there's little chance of fitting an audrino in my enclosure. I looked at the ad5259 because it had many more taps, 256...
  15. mathphobe

    Digi pot for pwm board

    Schoolboy error, my bad.. I was reading the highest number as the highest frequency, of course 2ms is faster than 500ms. Lesson learned! There's a lot of digi pots I could get, the 10k is an easy swap as there's plenty of ready made schematics around. I've chosen to use a 100k in place of...
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