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redwire

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Everything posted by redwire

  1. Hi DrinkH2O4, I don't know if anyone is going to try to match up parts on the board layout provided, to see what Picmaster changed from the design being discussed on this thread. It would certainly be easier with the sketch layout but you may need to pick a design and either ask Picmaster or this board for help. I thought Picmaster used a PIC chip to do some of the control work.
  2. redwire

    Hello

    Hello michaellot, Welcome to the board. Check out the blog and projects for some interesting builds
  3. Then why not eliminate D8, U1, R5, R6, and R4 and replace with one T0-92 that can handle a 40V input voltage that would get power from the 10V zener? These voltage regulators are pretty indestructible with thermal, voltage and current cutoff features. L7812AC.pdf
  4. What I was referring to was L7812 type. These have poor voltage regulation ?
  5. audioguru, Why is U1 and the associated negative and positive feedback necessary to output 11.2 V, used instead of a simple voltage regulator in the 11-12 volt range?
  6. Was your goal to provide a easy to build, basic PS or will this be part of a more comprehensive design that may include current control? I would have a concern about having the output shorted.
  7. I ran a test with a 0.47 10W resistor at about 1.2 V. 1.2/0.47 = 2.6 A . I only have it attached to a 100VA, 28V transformer so I guess it was about pegged out because the current control led did not come on. After a while, the heat sink on the one output transistor was very hot to the touch. U2 was warm. The BD139 was cool. U1 and U3 were warm. I then turned the voltage to 0.5 and didn't notice any significant change from the previous test.
  8. liquibyte, I had the boards made by a commercial pcb shop. On my other PS, I have (2) 2N5886G's on a aluminum heatsink about 4" x 7" x 1" with a small computer fan blowing across it. It is amazing how effective a small amount of air blowing over the heat sink is. I would not recommend containing the output transistors inside of the case without a fan. Others have mounted the transistors to the outside back of the unit. More tests tomorrow with low output, high current.
  9. One more picture of the rig operating
  10. audioguru, Finally got everything tied together for a quick test of the smd board. I ran a 3156 taillight bulb (about 2 A) for around 4 minutes. No heat sink on the bridge diode or BD139. The heat sink on the MJ11016 output transistor was quite warm, the bridge rectifier diode was very warm and the BD139 was cool. The hottest part seemed to be the 1.5K, 1/2 W transistor for the power-on led I added. Got a few more tests to run but it looks good so far. U2 was warm.
  11. On a MOT the secondary windings are very small wires with many windings because it steps up the voltage to thousands of volts. Remove these very small wires and rewind these. This should be consistent with many of the tutorials. The problem with using standard wire is that the insulation is thick and you will not get as many windings resulting in a lower voltage. Wires for transformer typically have a thin lacquer or enamel coating to allow tight, compact placement.
  12. liquibyte , I'm searching for some pictures of the final build but I haven't found any yet. I took a MOT from a large microwave (1100w) that I found at the dump. I removed only the secondary windings because the primary seemed large enough to handle the load. I purchased a thick copper tape that was approximately the width of transformer opening with conductive adhesive on one side and carefully doubled the thickness of the tape. I wasted a bit of tape until I got the hang of sticking both sides together. I wound the transformer using mylar tape ? between the layers of copper tape until it was full. I ordered the mylar tape slightly larger than the copper and may have had to trim the mylar a bit to fit the opening with. I can get 8 A at 12V but not at 50V. I don't recall the thickness(copper wt) of the tape or length but my intent was to have the cross sectional area equivalent to a 16 - 14g wire when doubled up.
  13. U2 Drives the output transistors. With a minimum gain of 1,000 for the MJ11016, a 3A output will require a 3/1000 = 3 milliamp current from the BD139. The BD139 has a minimum gain of about 40, so 3milliamps /40= nothing. The C-E saturation voltage for the MJ11016 is 200mA at 20Amps, so for max output the BD139 would have to provide 200mv. With a gain of 40, U2 would only need to provide 5 milliamps. I think the TLE2141ID can provide at least 20ma.
  14. I'm working on a smd version of this board with the TLE2141ID chip. The only thru hole components are the BD139, bridge rectifier, and R7. I plan to use a MJ11016, a darlington power transistor with a minimum gain of 1,000 in lieu of the 2N3055. Sure you may loose 0.7 volts on the output but with the 28V transformer there is enough headroom to still get 30V. I don't think the BD139 will even need a heat sink. Waiting on a few parts to assemble.
  15. Some accessories I'm working on. The display On issue when building the display is programming the chip. I'm building a board with smd components that uses the 32u4 breakout board from Adafruit. It can be programmed with a usb connector and does not need a special programmer. While simply buying a microcontroller is significantly cheaper, if someone does not want dive too deep into things this is an alternative. The lcd display can be mounted vertically or horizontally. Oh, the first line on the LCD displays the voltage. The chip senses when nothing is connected and displays the "connect wire" notice. It has outputs for a small fan, that can be set to turn on at a certain temperature or current setting. There are numerous "spares" that allows the board to be used for other purposes (operating a servo, leds, or other sensors).
  16. picotrain , The actual board layout has not changed since I posted the pictures in the first post. One or two part values have changed. I had several boards made if you would like to purchase one/two. I suspect it would significantly cheaper than getting 3 boards made. Send me a PM if you are interested. You have noticed that there is a missing 5.6 Zener. The reason is that about the time I developed the boards, Audioguru suggested using 2 diodes in series instead of the 5.6 Zener diode. Consequently, I prepared to board to use either 2 diodes in series or a 5.6V Zener. I noticed that the 0.47 Ohm resistor got quite warm and I wanted 5A capability so I used a 0.27 ohm resistor and it works fine. The trimmer allow me to set the max output for the transformer being used. I used a RS2005M bridge rectifier from Mouser. I had not installed the heat sink when I tested it and took pictures but I found a nice one out of an old computer power supply. I ran it with 3A without a heat sink and while it got very hot it didn't fail. Note that the ideal placement would be against the case. If you decided to do this, then simply run the 4 wires from the bridge rectifier to the board.
  17. gizmo322, try http://www.electronics-lab.com/projects/mcu/008/index.html. There is an AVR version out there http://www.electronics-lab.com/projects/test/007/. I'm working on a version that uses an Adafruit 32u4 breakout board and uses a usb cable to program, eliminating any expensive programing tools. While the breakout board is more expensive than the bare chip, programing is much simpler.
  18. What about Farnell/element14/Newark? very common part
  19. After adding the 10V Zener, I don't think R22 was adjusted on the parts list. Shouldn't R22 be approximately 1.5K.
  20. So you basically need a chip with random number generator to randomly flash the lights twice.
  21. redwire

    help

    Are you serious?
  22. Try an Arduino with a breakout board for the power supply, temperature sensor, and led (strobe). Do you know anything about soldering or programming?
  23. Yes, Some of the benefits: 1. Develop skills in making pcbs, and using software such as Eagle. 2. Learn troubleshooting 3. Utilizing a design (as revised) that is probably the best available 4. Ability to ensure quality parts are used 5. Satisfaction and pride in successfuly completing a project 6. Develop skills in understanding programming AVR chips (LCD Display project) 7. leveraging these skills to build other project using servos, lcd displays, flashing lights, etc http://www.youtube.com/watch?v=ryhK9xIUcrQ (sorry about the poor film quality) If price and time are your primary concerns then buying one a commercial unit would be your best option.
  24. denci, You should not need to change any parts to use the 3 MJ series transistors
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