TJ-067 Fan Control Mod for Precise Control - Page 2
- millcityroasters
- Posts: 253
- Joined: 9 years ago
Thanks, Slickrock. That's what I figured. I've got a pot and resistor squirrelled away somewhere on the landfill masquerading as my desk. I'll probably give it a shot and not tell Dave just to flummox him.slickrock wrote:It's set and forget. Absolutely no need to externalize it, so it's buried in the enclosure. No need to box it as the existing fan control is rather exposed to begin with.
- Boldjava
- Posts: 2765
- Joined: 16 years ago
NB: I will have mechanical abilities in the afterlife. Better yet, I will come back as a mechanic dressed in a blue shop coat with the Mill City Roasters logo on the back.millcityroasters wrote:... I'll probably give it a shot and not tell Dave just to flummox him.
Revenge will be a platter best served ccccold... <grins>.
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LMWDP #339
LMWDP #339
- millcityroasters
- Posts: 253
- Joined: 9 years ago
Hey, I'm just not tall enough to wear your BBQ apron. Besides that, the shop coat is dope, yo.
- slickrock (original poster)
- Posts: 272
- Joined: 13 years ago
Gary, as promised:drgary wrote:Where would I get those parts? And what does it look like soldered together?
Here's what the mod looks from the back of the panel (with panel unfastened and flipped over):
The stock fan control is the pot with the back side up and all the five panel switches can be seen all in a row soldered with bare wire (not part of the mod).
Here is a close up of the not very pretty electronics handiwork:
Keep in mind you don't need the big audio pot (the one with the knob facing up) for bias purposes - I just had that on hand after my failed audio pot attempt at improving fan control. You can get a way with using one of those small, flat, plastic linear trim pots for the job. The taper resistor I used here is huge for its intended purpose (That thing is about 35 years old - fetched it out of my high school electronics tool box).
Regarding parts sourcing, you can search Amazon (where I got the audio pot) or Ebay and pick up what you need.
07/11/1991, 08/21/2017, 04/08/2024, 08/12/2045
- drgary
- Team HB
- Posts: 14347
- Joined: 14 years ago
Since high school. No wonder this seems like second nature to you. Thanks, Joel!
Gary
LMWDP#308
What I WOULD do for a good cup of coffee!
LMWDP#308
What I WOULD do for a good cup of coffee!
- slickrock (original poster)
- Posts: 272
- Joined: 13 years ago
As mentioned in a previous post on this thread, I can think of a design that doesn't take away the very top-end of the fan speed, but IMO, operating the fan at top speed is way overkill for even hi-vent roasting on this beast. I only use top speed to quick-cool the roaster after I've finished my session.millcityroasters wrote: Quote taken from fan control malfunction thread:
I'm personally less interested in this mod because we've been experimenting with more airflow as a path to more clean sweetness and greater differentiation of flavors in the cup. This approach requires enough heat to support the increased airflow, but we've got an abundance of heat on tap and in many cases we're getting better coffee.
In any case, using the mod will reduce the near binary on-off sensitivity of the stock setup. Judging from the experience you shared via PM, perhaps the 750K Ohm taper resistor value may produce a taper that is sub-optimal for your setup. It's perfect for mine - I've put in some more roasts and I still grin every time I use the fan control. The control is very sweet and expands the hysteresis range where I can easily slow the fan down even enough to count the rotations by sight, yet I have the wide upper control in 50-100 range for medium to fast speeds. One recommendation here is to use something like a 1M Ohm pot as the taper resistor and trim the pot down until you get a taper that provides the widest range and control for your setup. As you drop the taper resistance you would need to trim back the bias resistor to keep the fan from spinning at the the 0 position. This approach would also allow you to squeeze out more top-speed from the fan.
07/11/1991, 08/21/2017, 04/08/2024, 08/12/2045
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- Posts: 228
- Joined: 9 years ago
Bookmarking this for my North 2kg.
Zero setting is actually level 30! 0-30 is just "off" for the fan.
Zero setting is actually level 30! 0-30 is just "off" for the fan.
- millcityroasters
- Posts: 253
- Joined: 9 years ago
What I meant by that post is we've been using the stock 30 as a low setting and increasing to more aggressive airflow than we had previously considered possible later in the roast with good results. This represents a slight departure from our previous idea of "low" airflow more conductive roasts.slickrock wrote:As mentioned in a previous post on this thread, I can think of a design that doesn't take away the very top-end of the fan speed, but IMO, operating the fan at top speed is way overkill for even hi-vent roasting on this beast. I only use top speed to quick-cool the roaster after I've finished my session.
In any case, using the mod will reduce the near binary on-off sensitivity of the stock setup. Judging from the experience you shared via PM, perhaps the 750K Ohm taper resistor value may produce a taper that is sub-optimal for your setup. It's perfect for mine - I've put in some more roasts and I still grin every time I use the fan control. The control is very sweet and expands the hysteresis range where I can easily slow the fan down even enough to count the rotations by sight, yet I have the wide upper control in 50-100 range for medium to fast speeds. One recommendation here is to use something like a 1M Ohm pot as the taper resistor and trim the pot down until you get a taper that provides the widest range and control for your setup. As you drop the taper resistance you would need to trim back the bias resistor to keep the fan from spinning at the the 0 position. This approach would also allow you to squeeze out more top-speed from the fan.
I'll try a 1M ohm taper though. I can see the benefit of a larger hysteresis and success would make me smile too. The 3 kg and larger roasters have VFD's making low speed control easy. More control is very likely a good thing.
- drgary
- Team HB
- Posts: 14347
- Joined: 14 years ago
Hey guys,slickrock wrote:As mentioned in a previous post on this thread, I can think of a design that doesn't take away the very top-end of the fan speed, but IMO, operating the fan at top speed is way overkill for even hi-vent roasting on this beast. I only use top speed to quick-cool the roaster after I've finished my session.
In any case, using the mod will reduce the near binary on-off sensitivity of the stock setup. Judging from the experience you shared via PM, perhaps the 750K Ohm taper resistor value may produce a taper that is sub-optimal for your setup. It's perfect for mine - I've put in some more roasts and I still grin every time I use the fan control. The control is very sweet and expands the hysteresis range where I can easily slow the fan down even enough to count the rotations by sight, yet I have the wide upper control in 50-100 range for medium to fast speeds. One recommendation here is to use something like a 1M Ohm pot as the taper resistor and trim the pot down until you get a taper that provides the widest range and control for your setup. As you drop the taper resistance you would need to trim back the bias resistor to keep the fan from spinning at the the 0 position. This approach would also allow you to squeeze out more top-speed from the fan.
For non-engineers (like me), could you please translate the following?
taper resister (and both terms independently)
hysteresis range
pot
"trim" pot down
bias resister
Gary
LMWDP#308
What I WOULD do for a good cup of coffee!
LMWDP#308
What I WOULD do for a good cup of coffee!
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- Team HB
- Posts: 5497
- Joined: 16 years ago
Variable resistors, also known as pots or potentiometers come in various tapers. The most common is linear, second most common is audio or logarithmic.drgary wrote:Hey guys,
For non-engineers (like me), could you please translate the following?
taper resister (and both terms independently)
hysteresis is a dead spot. In this case I assume it's how far you have to turn the to back to make a difference. In my experience mostly used on level sensing inputs to prevent chatter. Something turns on when the voltage reaches A but does not turn off again until the voltage drops to A - the hysteresis amount.drgary wrote:hysteresis range
A trim pot is a variable resistor used to set(trim) something and then usually covered up and never seen again. Often you'll find them sealed with drops of paint so they don't ever move.drgary wrote:"trim" pot down
drgary wrote:bias resister
A resistor that sets a fixed bias. In this case I believe it is the fixed 750K resistor plus the extra (trim) pot put across the original pot to lower the maximum resistance the original pot could reach. Two resistors in parallel have a lower resistance than either one alone.
Ira