Is this a brown out caused by the servo?


 
B

Brandon N

TVWBB Member
I started my test smoke with the servo and fan installed. All went well for about the first 30 minutes but then as the temp settled and I was the damper was near close I lost connectivity of my heatermeter. Did some debugging and found out if I disconnected the servo it stopped having issues. I replaced the servo with another, same thing. It starts working 100% but at some point it's like the servo shorts or draws too much current. From then on out this is it's behavior. The servo does still work as seen in this video.

Is this a brown out and I need a bigger PSU? Is there something else occurring?
 
Yes, the servo can draw a fair amount of current and can brown out the 1A power supply. When Bryan designed the HM it did not have the servo option, if he still has a 1A power supply spec'd in the BOM I think now that the servo has become common the power supply should be beefed up a bit. I anticipated taking things beyond the norm when I purchased my parts (I assumed it would be a bigger fan at the time) so I started out with a 2A power supply and it has work great for me (it only cost a buck or two more), but if I do plug in a smaller power supply I get brown outs too. It doesn't work as well for the smoker as it did for Van Halen... lol
Check around the house, 12VDC power supplies are pretty common, I've used power supplies from routers and hubs that have worked out too...
 
Last edited:
Hey, I just noticed at the end of your video you show the wiring cavity and it looks like the CAT5 jack is installed wiring side up, does it latch and lock in that position? The roto damper was designed for the latch side of the CAT5 jack to be UP, so you can push the latch down and unlock it. If your CAT5 jack pushes out when you insert the cable try flipping it around so the latch is on top and it should lock in place tight.
 
Ralph, I had it there to be accessible during the debug. It didn't latch there. I decided to wire 12v directly from my trolling motor battery so there would be no possibly of brownout. The servo definitely starts drawing too much amperage, so much so that the magic smoke started coming out. It looks like I'm killing the servos but I'm not sure why/how. I assembled the roto damper and backed the screw out to give it play. I messed with it in the house last night with no issues. I wonder if the heat is expanding the plastic just enough to cause a snug fit to the point that the servo damages itself. I killed 2 servo's today trying and on the second one I even used olive oil between the roto surfaces. I wonder if I also got a bad bunch of servo's or knockoffs. I ordered them from amazon.

http://www.amazon.com/MG90S-Micro-S...957&linkCode=ur2&showViewpoints=1&tag=tvwb-20
 
Did you correct your power supply issue? You need to start with proper power, IDK what letting the unit brown out over and over like that will do to it..
The servo sounded like it was moving without much resistance in your video, but kinda hard to tell. You shouldn't need any lubricant between the surfaces. For testing just press the roto damper together (and don't install the screw), the unit should move super easy at that point. I haven't had any problem with the plastic expanding and tightening down on the servo, but the servo hole size isn't very critical, so you can take a knife or something and scrape it out a bit unit the servo fits in there nice and easily. If the servo fits tight into the hole it will bind, though even in testing during the design process when I had things fitting very tightly I never smoked a servo...
Perhaps I should ask how/where you are connecting the servo? It needs to connect to gnd, servo signal, and +5VDC (not 12VDC).
 
With a good server I don't have the power supply problem or brownouts. Even connected directly to the 12v trolling motor battery I was getting "brownouts" so the servo was certainly shorting. It seemed to spin freely however I notice that it's getting caught trying to move off 0%. Even almost completely unscrewed it's getting stuck. It doesn't happen all the time but often enough. I'm thinking this is my problem.

RalphTrimble said:
Did you correct your power supply issue? You need to start with proper power, IDK what letting the unit brown out over and over like that will do to it..
The servo sounded like it was moving without much resistance in your video, but kinda hard to tell. You shouldn't need any lubricant between the surfaces. For testing just press the roto damper together (and don't install the screw), the unit should move super easy at that point. I haven't had any problem with the plastic expanding and tightening down on the servo, but the servo hole size isn't very critical, so you can take a knife or something and scrape it out a bit unit the servo fits in there nice and easily. If the servo fits tight into the hole it will bind, though even in testing during the design process when I had things fitting very tightly I never smoked a servo...
Perhaps I should ask how/where you are connecting the servo? It needs to connect to gnd, servo signal, and +5VDC (not 12VDC).
Click to expand...
 
If you rotate the servo (by hand) too far at a good enough speed you can kinda jam the gears on the servo, once that happens they seem to want to jam. I glue on the arrows and lines so I can see where the limits are to make sure I dont rotate it too far.
Where did you wire in your servo BTW? Are you sure there is no issue there?
 
RalphTrimble said:
If you rotate the servo (by hand) too far at a good enough speed you can kinda jam the gears on the servo, once that happens they seem to want to jam. I glue on the arrows and lines so I can see where the limits are to make sure I dont rotate it too far.
Where did you wire in your servo BTW? Are you sure there is no issue there?
Click to expand...
I ended up notching it right where the fan attaches so it's directly in the rear. There shouldn't be an issue there as it's completely loose. It was rotated by gear only, not by hand. I'm going to take a look at it in a few minutes to diagnose.
 
I got to looking at the parameters for the servo max/min pulse duration and I was way outside of the minimum (100 vs 500). I've changed it 800-2500. 2500 is the max so I'm pushing it there. I'll run it later this week and see how it does.
 
Brandon N said:
I got to looking at the parameters for the servo max/min pulse duration and I was way outside of the minimum (100 vs 500). I've changed it 800-2500. 2500 is the max so I'm pushing it there. I'll run it later this week and see how it does.
Click to expand...

You can calibrate your servo centre position by plugging it in without a pit probe attached. If your servo only needs to move 90 degrees, then you'll only need 500us of servo duration. Mine is set from 900 to 400.
 
I run mine at 740 - 2300 and Inverted....
While the damper is apart I make the blower speed go to 100% and then mate the two parts together so the two moons match (fully open). Set like this it should operate fully open/closed and within the range of the servo.
 
Awesome, thanks Ralph. That's pretty much the same procedure I used. I ended up with 800-2500 but I'll probably play with it a bit to make it more exact. Right now I'm cleaning the damper from the electronic smoke smell from burning the servo up with the trolling motor battery. I tried vinegar, soap and water, and now it's soaking in baking soda.
 
I'm sorry you had setup issues, I try to make sure to pass them on but for a while I had trouble keeping track of things because the forum private message storage is limited and I had to keep deleting messages to clear the box. That's why I moved over to the hotmail address. Sounds like things went REALLY bad if there is smoke involved, if you can't get things cleaned up well enough send me an email and I will set you up with some new parts....
 
Thanks ralph! I was thinking it was a brownout which is why I hooked the trolling battery to it. I was being stupid and should have used my brain. I'm sure things will clean up and work from there on out.
 
Ok, the smell is subdued enough for me to use it and I let it loose in the house from about 9PM to 12PM last night with the target set at the same temp as room temp so the servo would be moving a lot as the heater came on/went off. Seems to be working properly now.
 
Great to hear, hope you have better weather than I do so you can use it, it's sub zero here again today... Let me know if you have any more questions or problems.
 
Setup:
HM 4.0
Stock power supply
stock fan connected to HM via RCA cable

If I hook up the fan, it's fine. If I hook up just the probes its fine. But when my fan is attached and probes are plugged in, I get the exact same issue seen in the video. This seems to be especially noticeable when I have my pit probe plugged in.
 
What wiring scheme are you using in your cat5 cable?

Does the HM display and LED's flash on your unit like in the video? (indicating reset)
 
Last edited:
I am not using CAT5 - just an RCA cable connected to the Rpi's bottom port, right beside the power port.

and yes, the display and lights flash just like in the video.
 
You must log in or register to reply here.

 

Back
Top