04-10-2010, 01:55 PM
what pwm is is using a time `slice' of the voltage available
its how light dimmers, variable speed electric drills and even dcc speed control works
most things have inertia- electric light bulbs actually turn on and off 50 (or 60) times a second depending on if you are here or in the usa (commonly put on electrical equipement as 50 or 60 Hz)
do they look like they are turning on 50/60 times a second- no- they `look' like they are always on- thermal inertia in the filiment..
as an example light dimmers say..
turn it to 1/2 and the bulb gets half as bright
but modern dimmers (triacs) dont actually cut the voltage to half
what they do is apply the full voltage- but only for half as long on each cycle
it still gets the full voltage though
(its how dcc does speed control- it turns the track voltage on and off really quickly to the loco motor- if its always on in (as an example) 1 sec- then its full speed
if its on for 1/2 a second out of every second- thats 1/2 speed
etc etc
now do that tens/hundredsthousands of times a second and even though the motor is being turned on and off- its mechanical inertia makes it run- at full, half, quarter speed....
what I am thinking of doing is making the track voltage much higher
but using switching (magic black box bit) that only lets an `average' of 12v to the track- so the loco runs as it would on pure dc
( so instead of 0 to 100% time turned on, it would be 0 to say 5% time turned on- but that 5% of the time would be 12v...)
but the peak voltage would be 60-90- whatever volts- which would basically `punch through' dirt/corrosion etc
its a well tried and true technique- as far as I know tho it hasn't been used for model r.r before (at least not in the way I am thinking of using it)
its how light dimmers, variable speed electric drills and even dcc speed control works
most things have inertia- electric light bulbs actually turn on and off 50 (or 60) times a second depending on if you are here or in the usa (commonly put on electrical equipement as 50 or 60 Hz)
do they look like they are turning on 50/60 times a second- no- they `look' like they are always on- thermal inertia in the filiment..
as an example light dimmers say..
turn it to 1/2 and the bulb gets half as bright
but modern dimmers (triacs) dont actually cut the voltage to half
what they do is apply the full voltage- but only for half as long on each cycle
it still gets the full voltage though
(its how dcc does speed control- it turns the track voltage on and off really quickly to the loco motor- if its always on in (as an example) 1 sec- then its full speed
if its on for 1/2 a second out of every second- thats 1/2 speed
etc etc
now do that tens/hundredsthousands of times a second and even though the motor is being turned on and off- its mechanical inertia makes it run- at full, half, quarter speed....
what I am thinking of doing is making the track voltage much higher
but using switching (magic black box bit) that only lets an `average' of 12v to the track- so the loco runs as it would on pure dc
( so instead of 0 to 100% time turned on, it would be 0 to say 5% time turned on- but that 5% of the time would be 12v...)
but the peak voltage would be 60-90- whatever volts- which would basically `punch through' dirt/corrosion etc
its a well tried and true technique- as far as I know tho it hasn't been used for model r.r before (at least not in the way I am thinking of using it)
poopsie chicken tush