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  1. chopnhack

    Free MIT course on Circuits and Electronics

    Having been here for a few months I have seen other folks join with interest in electronics, but with limited or no background. I wanted to share this link with you and for anyone else who is interested. It is a course as described in the title of this thread by the Massachusetts Institute of...
  2. chopnhack

    Designing a Time Delayed Relay

    No, you have done more than enough Kris!! Thank you, I will need to do some more leg work from here on out until I become utterly confused and befuddled, which may not be long from now :D:p I will create a BOM and start on a new layout if you think the schematic is good enough to work from. I...
  3. chopnhack

    Best Low-Budget Printer?

    Thanks for the warning, not much for the romance novels ;-)
  4. chopnhack

    Designing a Time Delayed Relay

    The PCB has to fit inside a 10cm square box, there are some internal protrusions at the corners so, figure 8.8cm square. I was wondering more along the lines of the circuitry. I know the fitting will be trial and error with the layout.
  5. chopnhack

    Best Low-Budget Printer?

    Anything published yet? Can you provide a link? Both genres are my fav's :-)
  6. chopnhack

    Designing a Time Delayed Relay

    I figured on the component side, the bottom I envision mounting some low profile nylon bushing to keep the board from grounding out against the metal box or perhaps some threaded standoffs (like the ones used in pc pcb mounting to cases) with a nylon washer and nylon screw or just ensure no...
  7. chopnhack

    Best Low-Budget Printer?

    Take it for what its worth, if the machine has say 250k or more pages run through it - its probably due for a rebuild. Out of curiosity, what do you write?
  8. chopnhack

    Basic Electronics kit

    I am actively buying up all sorts of goodies from China-Bay, LOL - perhaps in a month or so, if the pirates don't strike I will have some fresh parts to play with! So far I have assortments of ceramic caps, electrolytics, pots, zeners, a 30x jewelers loop, diodes, battery holders, leds...
  9. chopnhack

    Best Low-Budget Printer?

    I guess it depends on page output, I have had inkjets work reliably for me for many, many years. Now that school is behind me I dont print as much. I can tell you that I have had the same ink cartridge in this machine for about a year. I have never had a cartridge dry up either. Laser printers...
  10. chopnhack

    Best Low-Budget Printer?

    For just general printing needs, assuming text, many HP Inkjet fall into this category and can be hand via craig's list in the us, ebay may be an option, but shipping could be prohibitive. I have a Deskjet 5150 that I have had for over a decade and it works flawlessly despite its age. Similar...
  11. chopnhack

    Basic Electronics kit

    Hey Dan, that is quite the assortment! At over $31 US I think I will make do for now with what arrives. I will let you know about the quality when they arrive for anyone that is interested. I am trying to spread the $ around to get a good kit together, don't want to waste money on trying to be...
  12. chopnhack

    Basic Electronics kit

    I found this on ebay from a supplier in Hong Kong http://www.ebay.com/itm/141019618980 I thought for $7.5 US it's not a bad assortment. Breadboard with 65 jumpers for about $6.5 US http://www.ebay.com/itm/121101205763 Thoughts on quality of the resistors? Can one assume since they are rated as...
  13. chopnhack

    Basic Electronics kit

    Adam, I sense a funny story coming on - explain how your auto destroyed your components :p:D
  14. chopnhack

    Designing a Time Delayed Relay

    Do you think the leads are tall enough for me to bend the transistor and heat sink back over the other components? "If so, with careful layout, its possible to have the transistor bend over other parts after they are installed." In other words, lay out some of the low lying items, smd caps...
  15. chopnhack

    Basic Electronics kit

    For the folks on the site that have built a few items, what would you tell someone to stock who has next to no parts? Is it worth spending a few dollars to buy a series of resistors? What range of caps would you recommend? Electrolytic, ceramic, tant? All kinds? Transistors? Diodes? Zeners...
  16. chopnhack

    Monster USB charger

    Perfboard can carry the 2a just fine, its the size of wire you choose to put across the perfboard that matters ;) A piece of insulated 22-20 ga should be ok for that load (23g will get it done but not much of a safety margin). I can't offer you any further advice, but I did come across some...
  17. chopnhack

    Constant current power supply

    An elegant and simple design, very nice Kris. Why are pins 5,6 of the unused op-amp connected?
  18. chopnhack

    Designing a Time Delayed Relay

    Fantastic Kris, thank you for the explanation and the pointer to capacitive reactance. I am going to check that out, very cool property!! I am understanding some things more clearly, but since there are more than one way to do something with electrical components, its not always clear. Case in...
  19. chopnhack

    Designing a Time Delayed Relay

    Diode Heat Dissipation: Lead Temperature should be determined from TL = θLA * PD + TA so for our example, 0.4w per zener, θLA assumed from a reference in MicroNotes 204 TL = 50 deg C/W * 0.4W + 25 deg C TL = 45 deg C Junction Temperature determined from TJ = TL + ΔTJL with ΔTJL = θJL * PD so...
  20. chopnhack

    Designing a Time Delayed Relay

    Thanks Steve, you are correct, I forgot it was rise above ambient! I will make some comments on the resource. I have read it over a few times!
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