On Sunday 02 March 2014 20:04:14 John Kasunich did opine: > > On Sunday 02 March 2014 18:12:42 Peter C. Wallace did opine: > > > On Sun, 2 Mar 2014, Gene Heskett wrote: > > > >> If you have a 5V push-pull output, another way would be to > > > >> connect this output to Cathode1 and Anode2 and connect Anode1 to > > > >> 5V through a resistor and Cathode2 to ground through another > > > >> resistor. > > > > > > > > But the i limiting R can also be in the common signal input line > > > > I'd assume? Or will that common voltage drop eat my lunch? OTOH, > > > > resistors in 500 packs from the shack are cheap. :) > > > > > > Sure, one resistor is fine for the second method. Slight advantage > > > of two is that the LED drives can be individualy adjusted. > > Wait a minute. It sounds like you are suggesting anode 1 to +5V. > Cathode 1 to anode 2, with a resistor to the signal source. And > cathode 2 to ground. That won't work, there is a path from +5V > thru both LEDs to ground, with no current limiting resistor. That > will let the smoke out of both LEDs. > Aha, yes, that was precisely what I had in mind. And now I see why you said 2 r's. I didn't grok that they would both be facing fwd voltages under those conditions.
> If you are using a single ended source, you want two limiting > resistors. +5V, thru resistor 1, to anode 1. Cathode 1 to anode 2 > and input signal. Cathode 2 thru resistor to ground. > > You can put the resistors on the inside if you want: +5 V to > anode 1. Cathode 1 thru resistor to input, then another resistor > from input to anode 2. Cathode 2 to ground. But you still need > two resistors. And I think this means there is a good chance on a couple microseconds of overlap in the on states at the output too, so some sort of a current limiter there would be indicated else it would seriously drain the limited 12 volt supply in the controller. Say about 1k ohms between the 12 volt line and the top detectors collector. The load R in the controller appears to be about 30k, so a 1k in the top will not noticeably restrict the top end. Due to the size & weight of the flywheel/fan, I have not explored the last 10% of the control range but I am sure the motor rpms have been north of 10k rpms in my playing as it is. That was at about 88 volts across the motor. The exhaust air from the fan cleaned the table off for about 18" around where the motor was laying, but the motor at that speed, was so well balanced that I could have walked away for half an hour and it would still have been laying exactly where I laid it when I came back. My scopes will be busy I think, while all this gets fine tuned. > If the input signal is differential, then you can hook the LEDs > back-to-back, and use a single limiting resistor. That I would have to build. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> NOTICE: Will pay 100 USD for an HP-4815A defective but complete probe assembly. ------------------------------------------------------------------------------ Subversion Kills Productivity. Get off Subversion & Make the Move to Perforce. With Perforce, you get hassle-free workflows. Merge that actually works. Faster operations. Version large binaries. Built-in WAN optimization and the freedom to use Git, Perforce or both. Make the move to Perforce. http://pubads.g.doubleclick.net/gampad/clk?id=122218951&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
