Building a servo controlled damper valve


 

D Peart

TVWBB Pro
I have received interest in the valve and control damper so I thought I'd start a thread with some instructions. I have placed an order for 8 of the valve (used all my credit at shapeways). I should get them in a couple weeks. I have some extra brass rod and would be willing the cut a length of it for people so that they don't have to go find it themselves. The cost is going to be ~$7 for the valve and rod plus shipping.

Here is how to put it together:

1. Drill a hole, centered, through the pipe, to insert the rod. This is the hardest part. To find where on the pipe to drill the hole, I slide the valve into the pipe and slowly rotated it around. Because the pipe isn’t perfect it fit more snuggly in some orientations than others. I found the orientation where the valve slid most easily into the pipe, marked it and this is where I drilled. I don’t know if this is actually required, but it is what I did. I drilled the hole using a drill press and a piece of aluminum channel as a v-block. Here is a picture of a v-block: http://littlemachineshop.com/products/product_view.php?ProductID=2186. The idea is that if you use a v-block, you can put the drill bit in the drill, and center the bit in the v-block. After doing this, when you place the pipe on the v-block it will also be centered. I started with a 1/8" bit I then made the hole a little bigger to provide a little slop which helped line up the valve better. The hole doesn’t have to be perfect because while the valve is perfectly round, the inside of the PVC pipe isn’t. Having the holes a little larger than 1/8” lets the valve fit better and turns more easily.

2. Put the valve inside the pipe and insert the brass rod through both the pipe and valve together. Check for alignment and clearance on the valve. The valve, when closed, should show little gap all the way around. If you are off center this is when you will see it. You can put the valve on a drill press and using a sanding block or file make it a little smaller if that helps. There is a hole in the center of the valve. Thread a 4-40 machine screw though it and put the screw in a drill press chuck. It will spin the valve nicely for you. Adjusting the valve size may help you get a better fit. Just be careful to not make it too small, as you can’t make it bigger later.  You want the valve to be close all the way around and touch the sides evenly. You can't get it perfect because PVC pipe isn't perfect. I would blow through the pipe when doing this to see how well the valve sealed.

3. Create the linkage from the servo to the valve. The length doesn't matter too much just make sure that it is long enough for the servo to operate through the full 90 degrees. To do this, set the servo at the 90 degree position, halfway through rotation and placed the horn on it vertically. Next, hook the horn on the valve such that it was pointed perpendicular (crossways) to the pipe. The valve doesn't need to be on the rod at this time you will adjust that later. We are just going measure how long the linkage needs to be. Measure the distance between the horn on the servo and the horn on the rod. This is the length of the linkage that you need to make. I make mine a couple different lengths both work anywhere from 1” to 2.5” will work. The diameter of the linkage will be determined by the size of the holes in the horn. I use a guitar string “A” string (0.032”). There isn’t really any stress on these rods so even smaller would work well.

4. Optionally, sand a flat spot on the pipe to mount the servo. I mounted the servo with some 100% silicone; it holds nicely and can be removed if necessary later for further adjustment.

5. With the linkage attached ensure that the servo horn vertical, and the rod horn perpendicular then adjust the damper so that it is 50% open, and tighten the machine screw to clamp it to the rod.

6. In the linkmeter options plage set the min/max pulse width so that the servo travel left and right equally from the vertical position. This means you will get about a +- 45 degree rotation for a total rotaion of 90 degrees. This will allow the valve to fully open/close.
Parts:
1. Valve
2. ~2.75” x 1/8” brass rod
3. 1 micro servo - http://www.amazon.com/gp/product/B006RCLJPA/?tag=TVWB-20
4. 3-4” piece of 0.032” guitar string
5. 2.5” – 3.5” piece of 1-1/2” PVC pipe.
6. ~1 hour of time to assemble


I'll add some pictures later today.

dave
 
Pictures
Setup to measure for linkage
IMG_4887_zps35700807.jpg


Kit includes:
1 - 1-1/2" PVC pipe cut to length and a hole drilled in the center
1 - 1/8" brass rod
1 - linkage (bent piece of wire)
1 - 3D-printed valve

Kit does not include:
100% silicon glue
micro servo

I'm going to sell the kit for $20 + $5 shipping (US). I only have 8 and 4 are already spoken for.

IMG_4890_zps2615963d.jpg
 
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3 Sept '13

I just sold my last kit and have nothing left. Hopefully those of you that got one enjoy them.

dave
 
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Thanks for posting this. The only thing it is missing is how to wire it up to the HM ;) I thought I had seen a thread a couple of weeks ago that discussed it but can't remember now where it was.

I have received interest in the valve and control damper so I thought I'd start a thread with some instructions. I have placed an order for 8 of the valve (used all my credit at shapeways). I should get them in a couple weeks. I have some extra brass rod and would be willing the cut a length of it for people so that they don't have to go find it themselves. The cost is going to be ~$7 for the valve and rod plus shipping.

Here is how to put it together:

1. Drill a hole, centered, through the pipe, to insert the rod. This is the hardest part. To find where on the pipe to drill the hole, I slide the valve into the pipe and slowly rotated it around. Because the pipe isn’t perfect it fit more snuggly in some orientations than others. I found the orientation where the valve slid most easily into the pipe, marked it and this is where I drilled. I don’t know if this is actually required, but it is what I did. I drilled the hole using a drill press and a piece of aluminum channel as a v-block. Here is a picture of a v-block: http://littlemachineshop.com/products/product_view.php?ProductID=2186. The idea is that if you use a v-block, you can put the drill bit in the drill, and center the bit in the v-block. After doing this, when you place the pipe on the v-block it will also be centered. I started with a 1/8" bit I then made the hole a little bigger to provide a little slop which helped line up the valve better. The hole doesn’t have to be perfect because while the valve is perfectly round, the inside of the PVC pipe isn’t. Having the holes a little larger than 1/8” lets the valve fit better and turns more easily.

2. Put the valve inside the pipe and insert the brass rod through both the pipe and valve together. Check for alignment and clearance on the valve. The valve, when closed, should show little gap all the way around. If you are off center this is when you will see it. You can put the valve on a drill press and using a sanding block or file make it a little smaller if that helps. There is a hole in the center of the valve. Thread a 4-40 machine screw though it and put the screw in a drill press chuck. It will spin the valve nicely for you. Adjusting the valve size may help you get a better fit. Just be careful to not make it too small, as you can’t make it bigger later.  You want the valve to be close all the way around and touch the sides evenly. You can't get it perfect because PVC pipe isn't perfect. I would blow through the pipe when doing this to see how well the valve sealed.

3. Create the linkage from the servo to the valve. The length doesn't matter too much just make sure that it is long enough for the servo to operate through the full 90 degrees. To do this, set the servo at the 90 degree position, halfway through rotation and placed the horn on it vertically. Next, hook the horn on the valve such that it was pointed perpendicular (crossways) to the pipe. The valve doesn't need to be on the rod at this time you will adjust that later. We are just going measure how long the linkage needs to be. Measure the distance between the horn on the servo and the horn on the rod. This is the length of the linkage that you need to make. I make mine a couple different lengths both work anywhere from 1” to 2.5” will work. The diameter of the linkage will be determined by the size of the holes in the horn. I use a guitar string “A” string (0.032”). There isn’t really any stress on these rods so even smaller would work well.

4. Optionally, sand a flat spot on the pipe to mount the servo. I mounted the servo with some 100% silicone; it holds nicely and can be removed if necessary later for further adjustment.

5. With the linkage attached ensure that the servo horn vertical, and the rod horn perpendicular then adjust the damper so that it is 50% open, and tighten the machine screw to clamp it to the rod.

6. In the linkmeter options plage set the min/max pulse width so that the servo travel left and right equally from the vertical position. This means you will get about a +- 45 degree rotation for a total rotaion of 90 degrees. This will allow the valve to fully open/close.
Parts:
1. Valve
2. ~2.75” x 1/8” brass rod
3. 1 micro servo - http://www.amazon.com/gp/product/B006RCLJPA/?tag=TVWB-20
4. 3-4” piece of 0.032” guitar string
5. 2.5” – 3.5” piece of 1-1/2” PVC pipe.
6. ~1 hour of time to assemble


I'll add some pictures later today.

dave
 
My Bad. Can't get to the wiki from work. Will take a look tonight and refrain from asking future questions until I get home and search the wiki. I hate wasting peoples time when the info is already there.
 
I'm wondering if you ever implemented the servo damper, if so, how did it work for you?

I had been completely uninterested in the damper setup because on my smoker the fan works great, it stokes the fire up like magic and holds the temperature rock solid with very little overshoot.

Last week I got a Char-Griller Kamado style grill, this thing is so tight and well insulated I am having a hard time hitting low temperatures unless the vents are almost completely closed. With my fan installed there is too big of an opening for convection flow and I can not choke down the fire enough to hit low temps. In general this grill needs very little air to stoke to temp, and burns very little coal. I think the blower will work fine for higher temps but it seems hopeless hitting low temps with the fan blowing the fire. I even choked down the inner diameter of the fan tube by about 90% and I still overshoot my target temp when its below 300 degrees.

I'm thinking a servo damper is the way to go for low and slow with this grill, so that's now on my to-do list. I've already ordered the servo's you linked from Amazon and will be working on this in the coming weeks. I just thought I would ask how yours worked out, and if there are any pointers you have for me.
Thanks
 
Yes I have received the kits ready to ship next week to all who are interested. I'll be responding to PMs with my paypal account for funds. The kit includes everything but silicone glue and the servos. I have more details above. These will be just like the one Bryan used to test with.

It'll take ~30 min (that is being generous) to put together. Since I've done it before it would take me about 5 minutes to glue on the servo and be finished with it.

dave

I'm wondering if you ever implemented the servo damper, if so, how did it work for you?

I had been completely uninterested in the damper setup because on my smoker the fan works great, it stokes the fire up like magic and holds the temperature rock solid with very little overshoot.

Last week I got a Char-Griller Kamado style grill, this thing is so tight and well insulated I am having a hard time hitting low temperatures unless the vents are almost completely closed. With my fan installed there is too big of an opening for convection flow and I can not choke down the fire enough to hit low temps. In general this grill needs very little air to stoke to temp, and burns very little coal. I think the blower will work fine for higher temps but it seems hopeless hitting low temps with the fan blowing the fire. I even choked down the inner diameter of the fan tube by about 90% and I still overshoot my target temp when its below 300 degrees.

I'm thinking a servo damper is the way to go for low and slow with this grill, so that's now on my to-do list. I've already ordered the servo's you linked from Amazon and will be working on this in the coming weeks. I just thought I would ask how yours worked out, and if there are any pointers you have for me.
Thanks
 
Is there interest for me to include the servos and just build the entire thing? It will add ~$10 to the cost and I thought some people may already have a servo and not want to pay that. I don't think I'm willing to do some with and some without I really don't want to manage that. If I get enough interest in the next day or so, I can order servos and build the units. I plan to ship next week.

dave
 
Dave,

I'd definitely like to have the complete kit with the servo included so I won't have to order it separately. Thanks.
 
I just got my servo's today and am starting to work with them. I'm not thrilled with the wiring method shown in the WIKI, would be nice if there was an actual header on the board for the servo. Would be nice if the blower connector design could be modified to work for the blower or servo?

It looks like the blower connector has +12V and the control line on it already, so the voltage would need to be changed to 5V and a ground would need to be added. Perhaps if the HM board is ever revised again a jumper could be added to select +12V or +5V on the blower(/servo) connector, and an alternate three prong connector (mini headphone jack?) could be fitted to include the ground needed by the servo? This way you would just have to change a jumper on the board to switch to servo mode, and the servo could plug right into the blower connector...
Not sure if there would be any way to accomplish this mod to an existing HM V4 board? I don't know well enough how the traces are routed, so not sure if changing from 12V to 5V would be doable without lifting the leg out of the board? What do you think Bryan?
 
No the wiring going to the RCA jack footprint is pretty specific to motor control, the "control" is actually floating and gets pulled to ground on pulse. The signal needs to be like high/low not float/low. Putting anything but a 3 pin servo plug on would be silly (putting a connector on that's not the right type that you have to solder a servo cable adapter on vs just soldering the adapter on) and you'd have a hard time fitting a 3 pin header in the existing footprint. Having a servo header is on the v4.1 idea list.

The part you don't see in the servo page on the wiki is that it ends in a 3 pin header. Take 3 pins left over from the pin header strip you used to attach the LCD, solder the wires to it, heatshrink, done. I filed down the blower jack hole in the case a bit to let the wires fit out so both blower and servo wires are accessible. Then use any standard servo extension wire to link to the servo. I made my own of those too because I will not pay!
 
Yes, I see that the control line is actually a controlled/pulsed ground. Is the pin on the mosfet that you connect to the servo control line not connected directly to the tip of the RCA jack?

If I am understanding you correctly, you are saying there isnt physical space available to mount a three pin connector (like a mini headphone jack) proabably due to the location of the 5V regulator right behind the blower jack? And no room to put a header to select the voltage anywhere?

It seems you have to cut the servo wiring harness anyway, to solder it to the board, and the wires on the servo aren't going to be near long enough to make it to the smoker, so you will have to solder an extension onto the servo wire. So you are doing all that anyways, soldering on a plug end (of whatever style) to the servo wire seems par for the coarse. It was my plan to cut the female 3 pin connector off the servo, solder it to the board and wire tie it down so it is secure, then solder a 3 pin header to the end of my extended servo wire, shrink wrap etc. I think that is what you were suggesting?

I still think the possible ways to make the blower jack be dual purpose blower/servo should be seriously explored... There are so many very small connectors available these days, there's gotta be SOMETHING with 3 prongs that will fit... Or even 4 prong, so there could be 12V and 5V present which would eliminate the need for the voltage select jumper. (and allow use of a 5v blower?) TBHWY I always thought the rca jack and audio patch cable was a kind of hokey way to wire the blower, I've seen others making similar comments about it.

EDIT: If you are suggesting to solder a male end header to the HM board to connect the servo I dont like that idea much, cause it will have a bare exposed 5V on it that could easily short out on something. That is why I cut the female end off the servo, soldered that to the board, and will put the male header on the end of the servo wire instead.
The reason I am thinking about an easier way to connect the servo is because I have a smoker that needs the blower and a Kamado that needs the servo, so I will be changing modes often enough...
 
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The MOSFET pin you solder the servo wire to is the gate pin, the input, so that's not connected to the RCA jack anywhere.

All the components are crammed in that space to the physical limitations of trace spacing and width. I spent 10-15 hours rerouting that board over and over and nudging components to get it all to fit without turning into a CF, as well as 2 physical PCB creations to test fit everything. And the 5V regulator still doesn't fit well! It will be rearranged in the v4.1 board.

The v4.1 board will swap the RCA jack for a 2.5mm barrel connector, and relocate it over by the probe jacks. The reason an RCA jack is used is because:
-- The blower doesn't come with any plug
-- I wanted something drastically different than the probes
-- I had plenty of old RCA cables around my house
-- I had an old RCA jack from soldering a coaxial audio input onto an old computer
-- Bingo! Precedent was set

Now that commercially available usable blowers are prevalent (only The Stoker had a blower and it had a "smart cable") I'm going to switch the connector in the next PCB. The auber and... one of the other ones are reported to having 2.5mm barrel jacks so that's going to be the standard. I don't want to build something with 3 pins and require adapter cables to be made for _both_ servo and blower. The wiring for the two is also so drastically different that none of the same pins would be able to be used. Any amount of components to try to sort this out would take more space than both headers would.
Blower: 12V, float/ground signal with cap
Servo: 5V, pulse signal, gnd

And yes I was suggesting putting a 3 pin male dangling off with chance of shorting to something. Mainly because it wouldn't require cutting anything and I knew that the v4.1 PCB would probably have a recessed male servo header (so that's what I do). But your idea is safer for now.
 
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I just sent PMs to everyone that PM'd me with interest in a kit. There were 5 people. If I missed you please let me know. I plan to ship them next week. Also before anyone pays any money to me I want to make one thing clear: I don't want to do this as a business, I have no desire to do so. I do have a desire for people to try to make the best BBQ possible and firmly believe that electronics can assist us in this endeavor. That is the only reason I'm building these. After I'm out of valve (3 left) I won't be making anymore, but the files are available online. I think it would be very easy to modify the design to make them easily printed on the home 3d printer. The valve design I made had an emphasis to reduce printing cost so it is a little overly complex.

The damper may take a little tweaking/adjusting to get it just right, but I think it is doable especially with the flexibility that Bryan put into the HM code. The biggest issue is to get the servo centered so that when it says it is closed, it is actually closed, not overly closed, not barely closed, but exactly closed. Open isn't as big a deal as most people will not be running at 100% and if it is not exact you won't notice it anyway.

Looking forward to others trying one of these out,
dave
 
I got the first kit shipped yesterday as it didn't need the servo assembled. I should get the rest out tomorrow if I can steal some time from the family this evening to finish them up. I had them put together but didn't like using silicone glue on the brass rod, so I removed it all and rebuilt using epoxy. This will hold much better.

dave
 
Thanks Dave,
Got mine in the mail yesterday, now for the time to finish it, looking to get clear pipe from scrap at my job, like your clear one.
 
I like the clear as well, but it is very expensive to buy.

I got the three others (complete) shipped yesterday. Hopefully everyone enjoys them.

I do have a 3-4 more, but I can't ship any until the end of July. If you want one PM me and I'll ping you when I can ship them.

dave
 

 

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