Servo upcoming pin change

Bryan Mayland

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ALERT! For those running servos on their HeaterMeters, there's a big change coming down the pipe you need to be aware of and adjust your hardware for.

Servo output is being moved from digital pin 5 (the blower pin) to digital pin 8

If you leave your servo connected in the way described in the wiki, it won't work and might burn out the servo motor. Any HeaterMeter firmware dated after today (20130725B) will have this change (revision B hardware only). Why am I screwing you like this? Well we all like the speed of using a fan to get the BBQ started, so I'm changing HeaterMeter to drive both simultaneously. This way you can use the fan+servo to start up the pit then disconnect the fan, or leave them both connected for double action.

I'll probably add options for "only run fan if output is 100%" and "fully open servo if output > 0%". That will allow the fan to only be used when the servo isn't cutting it, and the servo to be used as an on/off damper for the blower.
 

Bryan Mayland

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You just need to move 1 pin. There's no convenient source of 5V nearby so I recommend just leaving the power pins where they are and moving the signal to pin 14 of the ATmega (digital 8)


My servo died during my last cook due to some gunk getting wedged in the tunnel and preventing the damper from closing all the way. The teeny servo, bless its Chinese heart, tried to close it for several hours before I went outside and realized it had killed something. It makes a lot of noise but doesn't turn any more. I tested with a circa 1970s Futuba servo and it appears to work but this thing is about 10x larger than will ever fit to my cool BBQ servo damper.
 

RalphTrimble

TVWBB Diamond Member
Has something changed with the settings for the servo positioning? Running the last release I had 75 and 150 entered into the servo settings, now the servo just goes all the way in one direction and doesnt stop, sits there trying to burn itself up? I've tried all kinds of numbers and so far that's all I get?
The Pulse Width Range of my servo is 500-2400, I assume I was using 750-1500 in my previous setup (must have been X10?) but that wont work with this new system?
Sounds like the same problem Dan was having....
 
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Bryan Mayland

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The new system doesn't use the 10x multiplier so make sure you're entering the full values 750-1500. There may be an issue with it though so I'll hook it up to the oscilloscope and see.

EDIT: Confirmed broken! This is why you always should test after you make an insignificant change. Update the AVR Firmware "From online repository" to fix 20130731B
 
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Alan Erickson

TVWBB Fan
The new system doesn't use the 10x multiplier so make sure you're entering the full values 750-1500. There may be an issue with it though so I'll hook it up to the oscilloscope and see.

EDIT: Confirmed broken! This is why you always should test after you make an insignificant change. Update the AVR Firmware "From online repository" to fix 20130731B
Bryan. Does the picture showing the wiring on the servo page need to be updated (or perhaps label them V8 and low and V9 and higher)?

https://github.com/CapnBry/HeaterMeter/wiki/Servo-Mode

 

Bryan Mayland

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Oops yes it does. I'll fix it tomorrow. The picture 3 posts above is the correct wiring. No matter how much I update the wiki I just can't keep it all up to date when there's a new release. I'm forgetty.
 

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