Search found 2219 matches

by Robert Reed
Sat Jun 08, 2013 8:16 pm
Forum: General Discussion
Topic: Constant AC current ?
Replies: 8
Views: 2304

Re: Constant AC current ?

Have you considered constant current diodes? They are basically an FET with gate & source internally tied together resulting in a standard two lead diode package. I have never used one, but have been on the brink of ordering for past projects.If memory serves me right they were in the 20 ma range. D...
by Robert Reed
Thu Jun 06, 2013 5:24 pm
Forum: General Discussion
Topic: 800 watt LED
Replies: 3
Views: 1252

Re: 800 watt LED

Thats so typical of Lowes or home depot John. I think they dropped an M somewhere along the way (milliwatts?). BTW, they don't even mention what the power source is that it plugs into, just lines and lines of useless info!
by Robert Reed
Thu Apr 25, 2013 8:05 pm
Forum: General Discussion
Topic: Turning on a transistor abruptly ?
Replies: 7
Views: 2083

Re: Turning on a transistor abruptly ?

Zener would probably be better. They have very fast breakdown time. But remember that to convert a very slow rising voltage to a very fast step response takes a LOT of gain!!!!
by Robert Reed
Tue Mar 26, 2013 9:44 pm
Forum: General Discussion
Topic: Block Diagram Programs
Replies: 6
Views: 1744

Re: Block Diagram Programs

And to add - the blocks are as quick as pointing the mouse and square it. Then add one liners to connect them just as fast. Text any where you want. In 5 minutes you can have the total architecture for a fairly elaborate circuit. Love it!
by Robert Reed
Sat Mar 23, 2013 8:32 pm
Forum: General Discussion
Topic: Looking for ideas
Replies: 27
Views: 3826

Re: Looking for ideas

John Looking for ideas, short of going to 10 different frequencies. When you say 10 transmitter channels, are you referring to 10 transmit carriers or 10 different modulation codes independently sent on the same carrier frequency? Also did not understand about receiver operation. If a particular rec...
by Robert Reed
Sat Feb 23, 2013 6:06 pm
Forum: General Discussion
Topic: Sidetracked by the temperature
Replies: 5
Views: 1482

Re: Sidetracked by the temperature

In the span of all possible temperatures starting from absolute zero, it has always amazed me that in our little world of 100 degrees rail to rail how many things go wrong and KAPUT. Ain't cold a bitch! :sad:
by Robert Reed
Fri Feb 15, 2013 9:36 pm
Forum: General Discussion
Topic: Emitter follower as current booster
Replies: 57
Views: 20355

Re: Emitter follower as current booster

Eliminate the 50K pot. For the sake of example, lets say you had a 10 volt output at 555 pin 3. That would require a 1K series resistor in series with the 1K ladder resulting in 5V at the top. Use a precision resistor close in value but somewhat lower than that, maybe 950 ohm. Now add a 100 ohm pot ...
by Robert Reed
Tue Jan 22, 2013 8:45 pm
Forum: General Discussion
Topic: Electrostatic safety video ( youtube )
Replies: 5
Views: 1175

Re: Electrostatic safety video ( youtube )

Well, I guess thats all you can expect from a guy that has only one eyebrow - and ear to ear at that!.
by Robert Reed
Sun Dec 30, 2012 5:02 pm
Forum: General Discussion
Topic: B&D Gyro Screwdriver
Replies: 12
Views: 2230

Re: B&D Gyro Screwdriver

Could it be as simple as a spring loaded (return to neutral) potentiometer whose wiper turns with the handle twist?
Yee God-what am I thinking? No microchip and loads of software in this digital age, just can't happen!
by Robert Reed
Tue Dec 18, 2012 6:04 pm
Forum: General Discussion
Topic: 555 monoshot load design
Replies: 25
Views: 4133

Re: 555 monoshot load design

The Darlington arrangement is almost universal for driving the pass transistor in stable linear power supplies for 40 years. The 555 timer output is a totem pole arrangement and not a Darlington pair. I think you need new friends!
by Robert Reed
Mon Dec 17, 2012 9:00 pm
Forum: General Discussion
Topic: 555 monoshot load design
Replies: 25
Views: 4133

Re: 555 monoshot load design

If I recall correctly,the 555 output has a rather high rating (maybe 200 mA). This would certainly be sufficient to drive any BJT directly without the need for a Darlington arrangement. As Steve mentioned you could use a 3904, but better would be a 4401 in the same TO-92 case (it has a higher curren...
by Robert Reed
Sun Dec 16, 2012 5:11 pm
Forum: General Discussion
Topic: 555 monoshot load design
Replies: 25
Views: 4133

Re: 555 monoshot load design

You did not mention pulse requirements. So looking at the whole range of possibilities and for starters: Forget the op-amp. It will not be able to source/sink enough current thru those loads except at very low levels. Also the rise/fall times of the pulse will be markedly slower. Now as to the BJT c...
by Robert Reed
Mon Nov 26, 2012 6:51 pm
Forum: General Discussion
Topic: Would the US electrical code allow this ?
Replies: 9
Views: 2619

Re: Would the US electrical code allow this ?

How can you be sure the neutral will have enough voltage on it to drive a pair of LEDs? In an ideal world there is NO potential here. In my real world I have seen varying voltages present of almost zero to 2 vac. Always the neutral voltage is a function of load current in the TOTAL paths back to the...
by Robert Reed
Fri Nov 16, 2012 9:05 pm
Forum: General Discussion
Topic: 12VDC fan driven by 120VAC...
Replies: 9
Views: 1656

Re: 12VDC fan driven by 120VAC...

Edd
"Here in Tennessee, new construction the neutral and ground are not connected."

Don't understand that, as the neutral and ground have to be connected by rule of the NEC for years. Usually at the service entry point.
by Robert Reed
Sat Nov 03, 2012 6:10 pm
Forum: General Discussion
Topic: 120VAC pilot lamps are now led...
Replies: 5
Views: 1273

Re: 120VAC pilot lamps are now led...

You have done your math right. I suppose (1) 1/4 watt resistor and (2) 1N400x diodes could be squeezed into that housing.Would be poor engineering though and more like a product you would expect to find at you local Walmart :smile: