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  1. KJ6EAD

    Cordless 1500 Watt Hand-held Blow Hair Dryer

    If I were really going to try to improve the salon blow drying process for both the client and stylist, I'd build the dryer into the chair base, feed the air to a nozzle through a lightweight hose and put the dryer controls on the hose nozzle. The hose would never be in a position to damage the...
  2. KJ6EAD

    Help with LED strobe

    R4 and R5 differ because the forward voltage of red LEDs are lower than that of blue LEDs. The values are chosen to equalize current. In actual practice, an adjustment will be made "by eye" to match apparent brightness. The capacitors don't need to be physically large to have the correct...
  3. KJ6EAD

    Cordless 1500 Watt Hand-held Blow Hair Dryer

    Using Lithium ion batteries, you could drive a 1500W load for 30 minutes with a 15-20 pound battery pack. This could be worn in a backpack configuration. The battery pack would probably cost around $500.00. There would be no increased carpal tunnel syndrome risk but vertebral disk degeneration...
  4. KJ6EAD

    Mono signal won't work with a stereo aux in - no sound at all ?

    Can you check for opens, shorts and miswires in your cables and connectors? It could be a simple signal to ground type fault.
  5. KJ6EAD

    Assistance with Transistor Theory

    If I interpret the analogy correctly, Bob's making the point that both ways of modeling transistors have enough historical validity to work for construction of circuits; that it's mostly a difference in perspective (point of view) and semantics that results in people choosing sides and trying to...
  6. KJ6EAD

    Christmas Gift for my 15 year old electronics enthusiast

    Laser diodes are dangerous and not to be trifled with. A DVD writer laser is powerful enough to burn pits in an aluminum substrate and can easily blind. If your son is fascinated by light beams, get him some simple lenses with which he can collimate the light from an LED to make a "ray gun"...
  7. KJ6EAD

    Assistance with Transistor Theory

    The Wikipedia article on transistors is pretty good.
  8. KJ6EAD

    Advice on finding a part?

    Often when those break, the knob and wiper are what come off. If the resistive element is still attached to the board, you can probably measure it's resistance and get a good idea of it's value even while it's connected to other circuit components. Can you post a clear, well lit close up photo...
  9. KJ6EAD

    How to modify switch to always be on.

    A lot of people have been burned by heating pads. As a result they all have automatic shutoff functions built into the controls and thermal fuses in the pad body. You can certainly defeat all of these but the modifications will not be reversible. There are a variety of other heating pads, tapes...
  10. KJ6EAD

    Help with LED strobe

    U3 is one component shown on the schematic as U3A and U3B. The clock speed is controlled by R1, R2 and C1 as is typical for a 555 astable.
  11. KJ6EAD

    Help with LED strobe

    I used an old student version of Multisim to draw that schematic which is probably why the Qs weren't shown correctly. Some schematic symbols omit power pins so pin 8 is ground and pin 16 is VCC. Since we're nitpicking details of nomenclature now, the traditional method of describing pin to pin...
  12. KJ6EAD

    Help with LED strobe

    00, 01, etc. are not the pin numbers. They are the sequential numbers of the outputs. The pin numbers are on the outside of the IC outline. For higher powered outputs, use each of the existing transistors to drive the gate of an appropriately sized FET. The IRF610's shown in Kris' pod driver...
  13. KJ6EAD

    angle grinder soft start?

    You can buy it as a single unit but I've not seen one in that package. Most are in the form of a disk. Epcos make some that combine both features. http://www.epcos.com/blob/173714/download/6/thermofusevaristors-pb.pdf
  14. KJ6EAD

    angle grinder soft start?

    I believe it's a combination NTC thermistor and PTC thermal fuse. See references: http://www.ohioelectricmotors.com/what-are-thermistors-and-how-do-they-limit-inrush-current-702 http://en.m.wikipedia.org/wiki/Inrush_current_limiter
  15. KJ6EAD

    angle grinder soft start?

    Where is the part mounted and how is it connected?
  16. KJ6EAD

    From batteries to Wall power supply

    In your pictures of the battery compartment there's a piece missing that makes electrical connections to the batteries at the open end of the battery compartment.
  17. KJ6EAD

    From batteries to Wall power supply

    The voltage of that radio power pack will be too high unless modified; you didn't say what it is. Yes, you can make dummy batteries for connectors. I've done it before using end caps from old batteries, wood dowel and epoxy. You can use anything conductive that's the right diameter and length...
  18. KJ6EAD

    Where can I find good techno/instrumental music....

    Try Peter Hollens, Lindsey Stirling, Globus, Jean-Michel Jarre, Lesiëm and Magna Canta.
  19. KJ6EAD

    From batteries to Wall power supply

    It wants 3 AAA batteries, so 4.5V nominal but since a fresh alkaline battery can be as high as 1.7V, the device could probably handle an input of 5.1V without harm. Given this, I'd be quite willing to simply wire in a surplus 5V phone charger and call it good but if that scares you a little...
  20. KJ6EAD

    PCB Cleaning after Soldering

    That's fine. You should of course familiarize yourself with the best practices recommended by the manufacturer of your conformal coating.
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