On Monday 01 April 2019 22:16:11 Jon Elson wrote: > On 04/01/2019 11:27 AM, Gene Heskett wrote: > > I'd have done the same, except I'd have added a flyback diode across > > the solenoid to absorb the shutoff pulse from the solenoid. Perhaps > > with a small r in series to absorb more of the stored energy in the > > R. > > I'm pretty sure the diode must have been there, or it would > have only operated ONE time!
But thats assuming it was a fast switch too, Jon. Many times the response of the cell to the flame can be measured in seconds, and that would be a pretty slow switch. But I'd like to CMA with the diode anyway. Belt and suspenders approach. :) > >> Since this was in a safety system, I was a bit hesitant to > >> be so bold with this change, but, my circuit WORKED, the > >> original required frequent tweaking, maybe as room > >> temperature changed or like voltage changed. > > > > Actually, it seems like you did exactly what a good designer should > > have done in the first place. > > Yup, that's what I thought, too. > > Jon And yet, I have been plumb amazed at the stupidity exhibited in the finished product. Harris MW1A transmitter, designed for the 1 kw daytimers. Teeny little 100 watt motorised powerstat designed to be an automatic voltage regulator, run by a geared down electric clock motor. Stator contact, the ring the armature contacted, made out of aluminum by stamping. Took me a year of running the 3 miles out to the site because it was off the air, and finding it back on the air when I got there. Finally I decided to sit down in a chair and wait it out. Took most of 2 hours. The powerstat was losing contact at the slip ring. I put the circuit in straight thru connection and took the stat out and apart to find that ring burnt to ashes. A sliding contact, on alu? Boggles the mind. Even with a slather of deoxit on it is not going to work dependably, ever and certainly not for a year. I ordered a new stat from Harris as thats the only way I could get a pristine pattern, went to the scrap yard and got some sheet brass, and made a brass version to put in the new stat. AFAIK, its still working, maybe. If the whole transmitter hasn't been replaced in the ensuing time from '82 till now. It was Harris's first transistorized transmitter, and used the poorest transistors that would still do the job and the failure rate was pretty high when the stick it was driving had no coils across the eggs in the guy wires and was the tallest thing for a mile around in lightning country. Driver transistor failed, I went to the shack and got a cb radio final in a to-202 package. Only had about 10x the gain of the one Harris used, put it in and instantly made a 1600 watt transmitter out of it. Took half an hour detuning it to get it down to a kilowatt. And it did it on less amps into the finals, increasing the transmitters efficiency by around 10%. Typical, and I think that and the transformer debacle explains why Harris is no more. I told the guy who specced that transformer off explaining in great, but vulgar detail exactly what was wrong with his education. War stories. Been there, done that. Cheers, Gene Heskett -- "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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
