Servo and fan connections

I want to automatically "back down" the damper during/after a door open event to help with recovery times.

Does anyone run both the servo and fan together ?
The wiring would use a common ground, so I was wondering how you get that to work using the RJ45 pinout on one end while leaving the final 2 pairs open for future use...

Thinking of doing something like this:

. _____________________________________________ ||=== >> Fan and gnd*
.HM RJ45 <<====(standard ethernet cable)========**
. _____________________________________________ |||=== >> Servo, gnd*, +5v

Connect the ground lead* (pin4) of the RJ45 twisted pairs for the fan to one of the other paired wires where I would split off the 3 wires for the servo connection.

Also, what type of connectors do you use on the fan and servo end of the Cat5 ethernet cable?
On my smoker, I will be permanently mounting the servo to the damper and will need to use a connector, and can have the HM and fan removable even if the fan is soldered to the Cat5 cable.

Gary, did you see the Blower and Servo Wiring https://github.com/CapnBry/HeaterMeter/wiki/Blower-and-Servo-Wiring page on the wiki?

Also have a look at the various dampers on http://tvwbb.com/showthread.php?41158-so-how-are-you-attaching-your-blower-to-the-smoker

I'm using a damper with servo and fan. The design is on one of the threads and it has a RJ45 socket on the damper.

Good stuff Ron. Thanks for those links. I forgot there were several integrated blower/dampers out there. I will have both parts, just in different locations.

Looks like the ground is jumped on the RJ45 side on the wiki. The color code info and graphic there is really helpful too.

Working on my butterfly valves then I will be hooking up a servo on my stacks !

Thinking about using phone jacks for the individual fan and damper connectors since I have a crimper tool.

They should be pretty easy to protect from the weather when not in use.

Regular phone jack parts work great too. For example you can take a regular "phone extension cord" (just a phone cord with a male on one end and female on the other), add a "phone splitter" (male to two female), then cut the end off two normal phone cords and solder them to the blower and servo respectively. No crimps necessary and completely modular, just plug in the parts you want.

EDIT: Forgot to mention you can also run like 5 fans and two servos at the same time with the same concept. Phone splitters are all straight through so keep adding them and the only practical limit to the number of outputs is the total current draw, which should stay below 1A continuous.

5 fans on my smoker would turn it into a forge!

Bryan, I understand the 5 fans but two servos? Are the servos controlled individually? or are they in unison?

Rich Long said:

Bryan, I understand the 5 fans but two servos? Are the servos controlled individually? or are they in unison?

Click to expand...

They're in unison. There's only 1 servo control and 1 fan control circuit. Bryan's post falls into the category of "just because you can, doesn't mean you should"

Exactly, Steve_M!

The same signal goes out to every fan and every servo, but you can theoretically put a dozen of them on the same output using off-the-shelf phone splitters or simply twisting the wires together.

Butterfly damper mechanical layout questions...

1) Does the servo automatically go to 100% open or closed when power is applied to the HM ?

2) I want the arm on the butterfly shaft to be on the right side to make the right side of the blades go in the downward direction.

In the case where you could locate the servo above or below the shaft that turns the butterfly...

3) Should the servo be located on the top or the bottom of the butterfly shaft?

Edit: Found some configuration settings on another thread by Ralph T. where he uses 700 to 2200 inverted to give the full 180 degrees of motion ...

Sounds like the direction of servo travel can be reversed, is that correct?

1) Servo doesn't move until the first temperature reading on power on, at which point it moves to the appropriate position.

Yes, the servo direction can be reversed. To do that, check the checkbox next to servo that says "invert output".

Thanks Bryan,
I used the "invert output" to do my initial testing.
When powered on with just a pit probe and the fan going at 100% (because this is all on a table, NOT on the smoker) I just selected invert and saved the configuration and the servo jumped for me. I watched it close and unchecked invert and it moved back to the original position.

I found the Wiki page to be very good on the more techie details of servo usage.
That wiki page is https://github.com/CapnBry/HeaterMeter/wiki/Servo-Mode for those who are curious.

I have a TowerPro MG90S and use 1000-2000 for the pulse width and am getting a good 90 degree sweep with no buzzing.

After I got my wiring harness finished, I set up a test using a soldering iron, the pit probe, and the fan (running at 30% and inverted output to cool the pit probe since the soldering iron is providing the heat, but I had to block most of the airflow). Using this setup, I saw the HM modulate the servo as the pit temp hovered close to the setpoint. I tried some different settings and tried the 100% setting for the servo as well, just to see what it does. I will just use the defaults and see how it works on my rig.

The photos below show the wiring harness I built for my large cabinet smoker application.
Note: the blue shag carpet is in the garage, of course...


RJ45 and Ethernet cable with kind of a center tap for the servo connection using the 4 wire phone cord and a jack to the servo, which will be mounted near the exhaust outlet.
The Ethernet cable continues to the end where the fan+ is connected to one pair of phone wires and the ground is connected to the other pair of phone wires.

The phone wire is really tiny, so I wanted to double it up since I am running two fans. I think these draw somewhere around 500 ma.


The black stuff is permatex silicone... I tried using a drinking straw as a mold to cover the solder joints and had mixed results, but figured it may last longer than electrical tape.

oto of the servo damper and wiring harness on the cabinet.



Here is the servo motor and damper assembly. 1) open 2) closed.



This butterfly damper is made using a piece of 5/16 hard line. I used a cutoff wheel to put 3 slots in the hard line, one for each butterfly valve centered over each exhaust pipe. Cut a circle slightly smaller than the exhaust pipe and slide them into the slot. drill a couple of mounting holes for each of the butterfly disks, being careful not to bend anything. Use screws to mount the butterflies to the shaft, or use wire if in a hurry.

I drilled the shaft for the butterfly actuator arm, which is made from heavy gauge aluminum wire (easy to bend, but strong enough) with a loop at each end just a bit longer than the linkage on the Tower Pro part to get a little more rotation just in case. There is a nut for a spacer and then I put a screw in the end to keep the linkage from sliding or rotating. That made the funny angle so it has the handlebar mustache look.

The servo is mounted in the dry behind the exhaust cover, and I dropped the phone cable down to the connector about 4 foot below.

The linkage between the servo and the butterfly is copper wire and twisted to be just right. Can solder it to make it stay.