Unless the latter means an adaptive filter, I don't think such a unit would perform well.Originally posted by RobM (YankeeRob):
The speed control is done by varying the reference voltage on the second 555 timer. If this voltage was proportional to a difference in temp of a set point and an actual temp then this could work. ... The POT would set your desired temp. Maybe another POT could help control gain on it to ramp and dampen when you need to.
The issue is one of oscillation and lack of hysteresis. You turn on the fan, the flame blows sky high, you immediately turn down the fan, the fire slows and temp drops.
I can try to expand a bit.Originally posted by Bill Hays:
This is very interesting to me. I understand a bit about hysteresis, gain and what not but I'd like to hear more about how it works in this application. I've dealt with it in DC motor control over mechanical opposition, where mirror positioning is paramount (missile control) but I'd love to hear more about how this is controlled when you only have control of the fan feeding the fire and rely on snuffing the fire to cool it. I'm not a programmer, just into the electronic, and somewhat, mechanical end of it.
Bill
Originally posted by Amir:
Thanks for the invitation. One of my other hobbies is photography: both landscape and wildlife. I would love to come to Vermont one day and shoot the scenery and visit you all. I trust fall colors is the best time?
Originally posted by RobM (YankeeRob):
Most of the work I've done involving motor control and embedded systems was in college many years ago so I'm winging it on the linear circuit. I'm a business programmer for the most part. That said, I think the mods on that circuit could work but it wouldn't be an automated system - you'd have to control the gain/oscillation manually. I think there's quite a delay in time when the circuit wanted more heat and the feedback could deliver it. The circuit uses PWM to more precisely control the blower speed so it's not a hard on/off that the guru/stoker systems use. This is what makes me think that controlling the gain at the sweet spot with full fuel loaded would work. It would be a fun experiment. I did order the circuit - just need to come up with the mod.
-rob
Originally posted by RobM (YankeeRob):
Josh,
I'll check out your stuff. Seems from your posts here and on SMF you know a lot about probes and thermistors. I've been playing with a regular old kitchen probe like the wireless king you can pick up at WalMart. Do you have any idea on how to get a more linear response from these things? Is there an IC that can do this? It would seem so because these things are pretty at WalMart/Lowes.
-rob