You can drop supply voltage down with mere resistors in series and/or a pot to make speed variable. Ken
At 07:31 PM 6/9/01 +0000, you wrote: >Hi from Joe: > >Bob - placed an order, due in a wk; thanks for the tip, >sounds like what I need. They said $3.50 @. [800 826 >5432]. If you don't have an AC PWM controller already, >their cost is way more than the EM-114 sol'n. > >Re operation from 115 Vac - all modern drill motors, >etc. are run by pulse width modulation of the line >current, up to about 90% of the positive wave & for ac >motors both + & - peaks. They rely on the motor >inductance to smooth the current between on time gaps. >You'll hear & feel buzzing at low speeds w a drill motor >because the gap between pulses is large. Torque is way >down too, it's why the PWM process works as a speed >control. Don't need frequency change [for small loads >like this; I've dealt w them before & the entry fee >starts at about $500, WON'T work w permanent magnet >motors]. > >Re 6 Vdc supply - you'll find it hard to locate 1 w a >current rating of 1 amp; use of less will kill it in a >while [there's no internal protection for overloads & is >the most common death cause]. Besides, that exceeds the >motor rating by x 2 - 4 & has no current control, so >will cook the motor [if it survives that long]. Can't >use a zener diode to drop the supply voltage unless it >has a power rating of at least 1 W / volt dropped which >puts it out of reach [an industrial application]. Ex. - >if you have a strong 6 Vdc supply & need 2 V to the >motor, you would need 8 zeners in parallel to get the 2 >V w/o killing them [at 1/2 W each]. Guess it's feasible >but it's not 'sanitary'. > >Re train transformers - will need a rectifier diode to >make this permanent magnet motor run; 2 1N4000 in >parallel should get the power rating to handle the >continuous motor I. > >See? Bob's sol'n is pretty nice. Best I've seen. > >Bye. > > >-- >The silver-list is a moderated forum for discussion of colloidal silver. > >To join or quit silver-list or silver-digest send an e-mail message to: >[email protected] -or- [email protected] >with the word subscribe or unsubscribe in the SUBJECT line. > >To post, address your message to: [email protected] >Silver-list archive: http://escribe.com/health/thesilverlist/index.html >List maintainer: Mike Devour <[email protected]> > >
