Update on new stove control

[Snowy Rivers]

Got some work done finally on my new stove control panel.

Bought the switches, indicator lamps and other goodies.
Formed a piece of aluminum to replicate the original panel on the Whitfield 2T

Here is a piccy of the unit as far as I have it today.

Got the thing cut to fit in the stove like the original part

The lower large rocker switch is the main power and switches the neutral as well as the hot lead
The smaller rocker switch controls only power to the timer relay that feeds the auger motor (burner)

The red light will glow any time main power is on. Burner light will glow any time power is switched to the auger control relay.

The fuse is for the entire stove including the exhaust fan and the blower fan.

The red button is for the start sequence. (self explanatory)

The green lamp will glow any time the auger is on. (Blink on and off as the auger cycles)

The knob at the top is faked at present as I dont have the Pot for the fed relay timer yet.

The graphics (real deal stove control) are Possible and whatever,the panel will get a custom decal applied (local shop does that stuff) once the final parts are fit to the panel.


The draft/exhaust fan control and the room air blower control will be installed just in back of the control panel area in the side panel of the stove.

The control panel is just too small to allow for all the extra lights and the variable speed controls for the fans too.

The relay receptacles will fasten to the inside of the stove cabinet just behind the room air blower.

The side panel on this stove swings open easily with the removal of two scews and allows full access to the area for serviceing.


Still thrashing out the details on the draft fan speed contoller.

A triac speed control board is nice but adds a lot of complexity.

I found a company that makes a very nice small "Off the shelf" controller that they are sending me a sample of.

The room air fan control will likely end up being a standard casablanca fan contoller with manual stops placed on the knob to stop it from being turned OFF completely.

Once this setup is done the stove should have plenty of adjustments as well as parts that are off the shelf technology and can be replaced quickly.

The switches and lights are from Norvac and the control relays are coming from Precision timers.

Precision is also supplying the 5 position POT to control the fuel/heat range
Off time or burn time will range from 6 seconds on LOW to 2 seconds on HIGH
The actual feed time (auger on time) will be adjustable in the 1.5 second range

Currently with nut shells the stove really works well in the 5 second range for a nice medium setting and the 6 second range for a tiny spot fire. 3 seconds will get things up and heating right smartly.

The 2 second setting will likely never be used but the control comes with that resistor in it so ???


Hope someone finds all this interesting

Snowy

 

[lmjr]

Snowy,

I'm following this and find it interesting.

Question...Are you tying the auger and draft fan together with a single knob?...or are they two independent knobs?

It can be done either way but two independent Knobs would give user more to tweak with.

Even with only one knob there could be separate trim pots to still make initial tweaks and then sort of "set it and forget it"

The ability to at any time dial-in a sweet spot is nice, but would require a "cheat sheet" to refer to past findings.

And this may even reduce the stove's operation to only those "savvy" enough tweak it. Might even become a "one man stove".

I'll attach a sample wiring diagram of one knob does both auger and draft fan:

 

[Snowy Rivers]

My plan is to use a Pot to control the auger relay and with 5 positions 6-5-4-3-2 seconds of burn time between the auger feed.
Feed time at 1.5 seconds nominal.

The draft /Exhaust fan will be set up to run at a low voltaage of about 70 and a high of about 107

The actual fan speed in RPMs is probably more important.

The draft/exhaust fan will have a separate control with a graduated scale that relates (More or less) to the graduations on the fuel feed rate.

Currently the fuel feed controls the off time between auger cycles and each progressively higher feed notch increases the draft/exhaust fan speed a little too.

The actual fan speed does not increase a lot but it does increase.

Having the fan adjustable will make the overall adjustability far better.

I have toyed with the idea of using a 25 Ohm resistor and just running the fan at one speed that will be about half way between the current low and high settings and doing the fine tuning with the manaul draft control rod.

This idea has my attention as it would keep the components simple.

I may try wiring the draft fan up to a off the shelf variable fan speed switch and then running the stove and checking the fan speed with my stobe tach and see if I can find a sweet spot that will allow the use of a single speed and then control the air with the draft rod.

It would be easy to make a little indicator bar to fasten to the stove by the draft rod and have graduations on it that can correspond to a pointer on the rod.

Simply turn the fuel to the desired level and then place the draft bar to the proper spot and let it rip.

A comercially available Triac type motor control is available very reasonable at about $40 but I am still not totally convinced that all this complexity is needed to end up with a very reliable set up.

The one down side to using a resistor is the fact that it has to disipate the excess votage off in the form of heat.

The triac simply does the trick using pulse width modulation to maintain the desired voltage to the motor.

Overall the goal is to clean up the system and get things back to full function.

Currently the room air blower has basically one speed that it will operate steady at and that is about 2/3 of full speed I am guessing.

I am going to guess that the rason for this is a slow failure in the components that are tied into the Triac that runs the room air blower.

This whole mess is all tied into the fuel feed control.
The more fuel you ask for, the more draft fan that is applied and the more room air fan that is available.

Low fuel settings are supposed to allow a low fan setting and as the fuel setting gets higher the room air blower will only be allowed to go so low to prevent overheating of the stove.


The current fan speed of about 2/3 full speed is actually very good and the sound level is not bothersome at all even with the TV on.

I may just go with a choice of moderate speed on the room air fan and set it up so it comes on with the master switch and has zero adjustment ??????????

No matter, the room air fan can't be set so it can be tuned off though unless I wire in a snap switch to overide and turn it on full in the event of high heat in the convection plenum.

One step at a time.

The feed relays are a simple thing. The safety switches are easy too. 1 low temp cut off. 2 manual reset high temp switches, the pressure switch tied to the exhaust blower.


Thinking about installing a vacuum switch tied to the fire box to shut off the feed in the event of an open door or a failed draft /exhaust fan.

Currently the stove will continue to feed even with the door open. I dont like this.

A micro switch would fix the door issue but not the failed fan thing. Having the stove smoke the house all up is not my idea of fun..

Several stoves use a neg pressure fire box and the switch could be easily adapted from one of those units..

Once the burn season is fully done with, I can get into this beast and rewire things to my likeing.

The new hearth allows me full access all the way around the stove with ease.

This was done with the rewire and mantenance in mind. My old stove was so tight to the wall that getting into it was almost impossible..


I can lay on my side and slide under the vent pipe and access all the way around the back of this stove with ease.

Gonna be fun for sure.

I love a challenge.

Best, if it all works as I plan eh :cheese:

Snowy

 

[jtakeman]

Add me as a follower! Definely interested in your venture.

 

[Snowy Rivers]

I will post more info and piccy's as they happen.

until we are completely out of burn season I will leave the stove unmolested.

Once burn season ends (mid May) I will then take time to look over the wiring in the stove real well.

Looks like I may be able to tie into the exsiting wiring with ease and safe having to completely rewire the thing.

My goal is to be able to use the same type of Molex connectors and just add these to my new control "harness" and then just plug the new controls into the stove.

I currently have the rear panel off the stove (removed it while diagnosing the smoke leak) and the fan motors run a lot cooler with this off.

Thinking about making an aluminum expanded metal cover to replace the old solid one.

This will keep little fingers (have grand kids) out and yet afford good airflow.

Not a hard job at all to do this.


The stove sits such that there is not a view of the back from any angle. Only way to see the back is to get up on the hearth and look back in there.

Later

Snowy

 

[smwilliamson]

Are you still using the MK gear motor? I like to the electronic aspect of your work but wonder how the relation of auger gearing may play into your heat controls. Is the motor on the Whitfield a 2rpm?

 

[Snowy Rivers]

Not sure if its an MK motor or not.
Whitfield used a 1 RPM motor.

I am not going to change the speed of the auger or the amount of time that it runs each time its on.

On for 1.5 seconds feed time and off for between 2 and 6 seconds.

The goal is to just make the system more reliable and not to actually change the way it works.

Snowy

 

[smwilliamson]

I can't find the thread where we were discussing it...sorry.

If the problem with TRIACS sending a half phase which blows out a motor...couldn't a relay be installed to avoid the perishing of the motor?

 

[Snowy Rivers]

There are several ways to protect the motor, the issue is the initial cost incured to build the stove in the first place.

The manufactures have gone to great lengths to cut manufacturing costs.

Much of this is "CHEAP" electronic controls that are all probably made over seas for their exact stove.

The addition of an extra part to protect the motor may end up costing a $ so multiply it out.

You and I get to pay the bill for the new control board and the new motor and the company gets to make a bunch more $$$$ (Most probably the stove will make it through the warranty period before the electronics die off)

I am seriously looking at adding a single resistor to the draft fan circuit and running the fan in the middle of its current speed range.

The air supply can be controlled simply by adjusting the damper control instead.


I hate to add more electronics to protect the electronics. Its a vicious circle with no real end.

Sort of like the dog chasing its tail.


If a single system is not good, add double redundancy, then to be sure its safe add more safeties and more complexities.


The original concept of the pellet stove was a simple device that could efficiently burn compressed wood pellets without the hastle of chopping, spliting and handling fire wood.


That goal was accomplished quite a few years ago. Then along comes the notion that we have to add a computer to the thing to make it so easy to use that you dont even have to light it anymore.

SOOOOOOoooo now the thing has become so complex that it is far more vulnerable to failure than ever before.

I used to be able to keep a very small amount of spare parts in a box up in the cupboard for the pellet stoves. Now the cost for that box of spare parts is in the many hundreds of $$$$$

Now back to the original thought.

The triac being an efficient way to control the speed of the fan motors is great, the issue is the quality and size of the components used.

These control boards that we are expected to pay many hundreds of $$$ for cost the manufactures nowhere near the numbers we pay.

Profit margin at the manufactures level are pretty good.

I have found a company that makes Triac based motor control boards that can be purchased for about $40

This should say something right here.

The basic stove control has a timer to control the feed motors on time and off time, the ability to control the draft/exhaust fan and the room air blower.

There is a circuit to start the stove and get it to temperature and a couple safety switches.


Just way to basic of a need to add more complexity.

On the cold dark and dreary night in the middle of winter, I personally dont have any desire to deal with a complex issue when it comes to my "Camp Fire"

Some say I am just too old fashioned, well I disagree, we have become as a society, far too dependant on the computer to do everything.

As soon as the micro chip got rolling good, the engineers just had to install one of more into everything they could get one in.

I have an old Kelvinator refrigerator that was my folks and it was made in 1940. Runs just as good today as it did when they bought it back in 40.

Does not have a micro chip anywhere in it. How did they ever survive ????


Snowy

 

[jtakeman]

snowy,

How's the new control coming along??


jay