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  1. M

    Need help using Nichrome wire for a foam cutter

    ....and who makes an untried cut on a new prototype? You test it on scrap!
  2. M

    Need help using Nichrome wire for a foam cutter

    Since when is it a complication to give some one an option? I didn't slam Colin's method; it will work. Not knowing anything about Ian....he might be a 13 year old kid with that "little knowledge" that Colin implied that I had. Then to suggest to this person to use a lamp dimmer that runs off...
  3. M

    Need help using Nichrome wire for a foam cutter

  4. M

    Need help using Nichrome wire for a foam cutter

    as I said I do make mistakes it should be... p=3.5(i*i*r) :)
  5. M

    Need help using Nichrome wire for a foam cutter

    Hello Duke, Glad you could join our friendly discussion. P=IE vs P=i*i*R The later contains the variable R, which you have to change during the computation between Colin's solution and mine. Colin's will require 3.5r and i, while mine requires e, 3.5i, and r/3.5. To calculate with the i*i*r...
  6. M

    Need help using Nichrome wire for a foam cutter

    If That is correct. You are telling him to change the voltage by a factor of 3.5 making him buy a new transformer. Whereas I'm saying to change the current by changing the resistance. I know that I have more nichrome wire than I do various transformers. And not knowing someones background and...
  7. M

    Need help using Nichrome wire for a foam cutter

    The power density needs to be the same and I stand by that. I typed the response very quickly; I'll have to go back a check it and admit anything that's wrong. However, you took exception to my statement " to get 3.5 times the power you have to have 3.5 times the current." Your comment to...
  8. M

    Need help using Nichrome wire for a foam cutter

    You sir know not of what you speak. I You sir know not of what you speak. I have designed and built and use them quite often. I have three in my shop as I type. I am not misusing anything. You said I was full of rubbish. What I said is correct. And it works very well.
  9. M

    Need help using Nichrome wire for a foam cutter

    I just checked to see if they've changed what was in all of my text books and according to http://ewiaei.org/formulas--laws.html , they still use the same formula for power. Pwatts=Voltage X Current. And I know they haven't changed the algebra or are you saying that they have changed algebra too?
  10. M

    Need help using Nichrome wire for a foam cutter

    Really? The last time I checked P=IE So 10a x 10v=100w 3.5 x 100= 350w (3.5x10a)x10v=350w maybe my calculator does work anymore. So yes if you need 3.5 times more power you need 3.5 times the current.
  11. M

    Hantek DSO5072p Oscilloscope?

    It seems descent to me. I have 40years in electronics. The Naval Aviation Tech Training Center (NATTC) uses a Vigilant or similar and the Hantek seems to be as good on the outside. I haven't opened yet, but it feels(knobs) like a good piece of equipment. Just like cars, shoes, clothes...
  12. M

    Need help using Nichrome wire for a foam cutter

    POWER DENSITY...watts/ ft, or watts/sq in., or sq meter. power density! Your 1' wire at 18v has a certain amount of power/ft. You are increasing the length by 42/12 = 3.5. So now you need 3.5x the power. But you've also increased the resistance by that same factor of 3.5 To get 3.5 times the...
  13. M

    Running two separate LED strips from a set of 3 at the same time.

    Based on what's been said in this post ...and like Harold and Lightning said.... you have 3 mosfets. Connect all source terminal to ground (I'm assuming you are using N channel logic level Mosfets), connect the drain of the mosfets to the black wire on one of the LED strips, and connect the...
  14. M

    Building a very basic project but need help

    Not really sure what the LED is for, but for a quick and dirty thingy with a flashing LED...there are so many little things that have flashing LED. Lapel pins, Mardi Gras beads, LED Christmas necklaces, LED rings...... Just take one of them and hack it. If you want to get fancy program an...
  15. M

    Hantek DSO5072p Oscilloscope?

    I have the 5102B. The B is more storage and it's worth it. Love my scope. There is supposedly a hack that will turn any of the scope into the 150, 200Mhz. just by changing a file or two on the scope. It's all controlled by the software. The hardware is the same except for the amount of storage.
  16. M

    Potentiometer as a Variable Resistor

    The simplest thing you can do (and it's pretty cheap too)...
  17. M

    Ultrasonic sensor working underwater?

    I have used that waterproof transducer and it works ok, but it's blind from 0-25cm(check the specs on ebay). The one I used actually worked to about 20cm. Once your less than 20cm, the reading were erratic and in the range of about 90cm (if I remember correctly). Because sound travels faster in...
  18. M

    Problem: Schmitt Trigger not giving ON/OFF output

    You can make a Schmitt using an inverter cmos gate. As was posted, the 741 cannot swing withing 2 volts of the rail. So using ground and a 5 volt supply, you only have a 1v swing. Depending on the hysteresis of your circuit, you may not be able to overcome the feedback signal...
  19. M

    Long duration timers - Notes for beginners

    The easiest way to do a long timer and most accurate is to use a uController. I use Arduino pro minis. just using millis() will give you a 24day timer. Add a loop counter to the program and you can go up from there. 10 times through the loop and you have 240 days. You could also use one...
  20. M

    LM386, MIC Help required

    add input bias resistor I've looked at the data sheet for the LM386. For your set up, I think that you need to add a 10k resistor from the input pin to ground. If your gain is not high enough you can add a cap across the two gain pins. Check the data sheet. If you have a scope check the...
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