The Shop > Wood & Stuff
Drum/ Thickness Sander
Bluechip:
Nope ... Should be Linear. The frequency would drop very rapidly as the resistance increases.
eg ... say you had a 100k log pot the resistance change for the first ( say) 10 deg. would be a whole lot less than the last 10 deg.
Have not used 555's for PWM for ages, gone onto PIC uControllers .. Smartarse :D
IIRC this is the cct. I used to use .. is it the same as yours ...
Dave
EDIT Rb is a linear Pot ....
Or it might have been this ... :scratch:
S. Heslop:
Whew, was worried i'd bought the wrong kinds of pots.
Microcontrollers are my eventual goal with electronics, but I figured it'd be best to figure out how discrete components work first. In the past i've tried reading books on the subject, but i've never found much stuff that isn't either incredibly theory heavy with little practical stuff, or stuff that just shows circuit diagrams with no explanation as to what anything does.
Thanks for the diagrams though. I'll try them out and see how they go.
Bluechip:
Most of the stuff you need to know about '555's in here :thumbup:
http://www.amazon.co.uk/Integrated-Circuit-555-Projects-BP/dp/0859340473
PS The two BATxx Schottky diodes can be 1N4148's, makes no significant difference.
IIRC the 2nd circuit does not affect the base PWM frequency ...
Dave
S. Heslop:
That second diagram works much better at controlling the speed. Also produces a nicer square wave without the high points (inrush?). It does change the base frequency though, but i'm not sure if that is really a problem.
Bluechip:
It may well alter the frequency a bit ... it's a good few years since I did PWM with a 555.
Once you get into PWM on PICs its much more stable and very easy to change by code rather than oiking out the soldering iron.
If you're using breadboards I wouldn't bother about the glitching .. it does happen as you have a poor layout and contacts. Been there many times looking for non-existent problems ... :palm:
If you want to 'scope it I would swap the motor for a resistor, no noise/ spikes from the commutator, and the sync. is better.
Post your original circuit ???
Dave
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version