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  1. bahstrike

    Joining w/ external GND killing my PSU?

    This particular one is solved. Turns out the cable for another connected device was tying my -12v to chassis. On it's own, this was "fine"  and didn't really cause a problem. The problem arose when connecting to the external device, which ties its (and my)  0v to chassis,  thereby completing a...
  2. bahstrike

    Joining w/ external GND killing my PSU?

    I'm continuing some investigations and found that the external device ties its DC GND  to  the actual case Ground.  Should I be doing the same?
  3. bahstrike

    Joining w/ external GND killing my PSU?

    Hi all, I have a device that outputs a regulated +12, -12, +5v  supply for it's own use. The current design ties GND to the center-tap of the transformer. This device detects a low voltage DC signal from an external source. To provide a common reference, I tie my GND to external source's GND ...
  4. bahstrike

    failed RS-232 level converter :(

    Thank you Hero, I really like V2 for the benefit of no switching waste.  I'll try that design with my next attempt at a DC->AC  coil driver, where higher currents are necessary. From simulating, my existing receiver  (RS232 -> TTL)  should work OK with ~8mA maximum switch waste (on...
  5. bahstrike

    failed RS-232 level converter :(

    I was under the impression that if base voltage is equal to emitter voltage, the transistor is totally off and the collector is essentially high-Z. That's why I have pull-ups on base-emitter of most transistors. So you're saying that I basically have current flowing from pull-up of...
  6. bahstrike

    failed RS-232 level converter :(

    I have a circuit that already provides +12 and -12 volt supplies. The microcontroller Vdd is 3.3v. I tried designing a transistor / resistor system to handle the invert and voltage shifts, without using a MAX232, but unfortunately it does not work..  It overheats and I could only salvage the...
  7. bahstrike

    simple voltage detect - wide range

    For this project, I only want to detect the presence of a voltage, regardless what that voltage may be.
  8. bahstrike

    simple voltage detect - wide range

    In this project, it's OK to draw current from the source. But in my next project, it's NOT OK to draw any noticable current, so a true DVM would be applicable.  Luckily for that scenario, I can pretty much gaurantee the voltage will be between 5v and 24v DC,  therefore electrical isolation is...
  9. bahstrike

    simple voltage detect - wide range

    ???  I don't know what you mean by constant current source. Is it a special component, like a Current Sense resistor? The 5v - 240v  is generated by a 3rd party device that I don't control, and the voltage level may vary depending on the manufacturer so I cannot predict what it will be. ...
  10. bahstrike

    simple voltage detect - wide range

    DVM circuit would be wonderful. I seem to have found DVM schematics with either a lot more components, expensive ICs, or ones that are based on ICL710x which has an integrated LED segment driver..  far beyond my needs of a simple  on/off. I figured that by using reed relays with varying...
  11. bahstrike

    simple voltage detect - wide range

    I'm trying to simply detect the presence of a voltage,  either AC or DC,  across a wide range  (5v through 240v). I attached a picture of my current schematic.  LTV817 opto-isolator gain should be around x10. However I think I can simplify this design to fewer resistors and relays. Range...
  12. bahstrike

    dual-output transformer

    thanks for the assertion guys
  13. bahstrike

    dual-output transformer

    KevinIV: its alright, the diodes are actually the DB104 chip  (bridge rectifier  1A 400V). the current consumption predictions I made were only to show that the Top-Center  output (~2.4 watts)  is a lot higher than  Top-Bottom  (~0.84 watts) ..which leaves the bottom half of the coil used at...
  14. bahstrike

    dual-output transformer

    I have a 12VA CT transformer,  from which I would like to get both  24vdc and 12vdc. As shown, I use Top-Center to get 12v,  and  Top-Bottom  to get 24v. The transformer is rated for  500 mA @ 24v series output,  and  1 A  @ 12v  parallel output. I expect to simultaneously draw maximum  35mA ...
  15. bahstrike

    digital x-ray

    although i consider you guys to be the masters here, seeing as it's an electrical engineering website..  i still want to toot my programming horn! please check out the video for a 1-minute demonstration of instant digital x-ray.  i have reasonable understanding of the internals of the devices...
  16. bahstrike

    where i work (pic)

    its finished now (see pic), but i didn't plug in the power yet. first, of course, i need to check most (if not all) connections. already i had to use an exacto knife to clean between several traces, before adding components.  for typical signal routes on a self-done PCB, i use 12.5mil wide...
  17. bahstrike

    where i work (pic)

    also comment on safety-  we have appropriate shielding  (lead apron and portable lead wall are used)
  18. bahstrike

    where i work (pic)

    sorry, i admit this is mostly a useless post.  im really excited about the parts from digikey coming in  ;D ;D    i also installed new triacs to improve my reflow oven-  testing that tonight!!
  19. bahstrike

    where i work (pic)

    log in to see pictures of my office!  the software seen is my first ever C# project,  although i've got plenty of C++ experience (among other..) the xray on screen is of my own right hand, but from a few months ago.  the X-CELL unit (in picture) is a real xray machine but it is usually not...
  20. bahstrike

    ethernet portal circuit

    updated circuit-  includes audio amplifier shucks i gave my idea away  XD i have drawn the path and labeled the audio's form, starting at the network connection to the device's speaker
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