servo/fan problems in RD3


 

ChrisMueller

TVWBB Member
Hi all. I've been running my heatermeter setup for several years now. I got a RotoDamper from Ralph probably 2 or 3 years go. Things were going great until a few weeks ago. I noticed the vent door wasn't opening properly anymore. Sometimes it would open a little, sometimes it wouldn't move at all, other times it moved but all over the place. I noticed my CAT5 cable I was using had some cracks in it, so I replaced them hoping for a fix and it seemed better at first. But then it came back.

It kind of seems like maybe I'm having a power problem. If I twist my power cable plug around in the jack on the heatermeter I can sometimes hear the fan spin up faster or slower.

What should I do to track this problem down? Should I just get a new power cord? This one is a UL listed power supply from an old portable hard drive. I can probably find another in my supplies, so maybe that should be my first try. Otherwise, can I measure voltages somewhere? Or should I just assume a bad servo in my RD3? I do leave that thing attached my my Green Egg all the time.

Any help is appreciated.
 
If you have another power supply to try you might give that a shot, cause the fan changing speed when you move the power jack is kinda odd. If you've had the unit for years you might want to make sure nothing has gotten gummed up and sticky, or tightened up on you. You want to make sure the valve still moves freely. If all else fails you might try another servo...
You should also look inside the CAT5 jack on your HM and RD3 to see if there is any corrosion there, after years outside this could become an issue.
 
Thanks Ralph. I didn't even think about looking inside the RD3 wiring. Not sure why. I pulled it off this evening and looked inside and found a bunch of frail wiring. The CAT5 jack wasn't in bad shape, but a couple of wires pulled free with little to no force. I think I need to rewire this thing with some better wire. I used solid UTP Cat5 last time. Perhaps I should use stranded.

Either way I think if I fix this mess inside my RD3 wiring, I should be good.
 
If you would like something more robust, then you should think about using one of my adapter boards. It had a cat5 jack soldered unto a pcb, along with a Thermocouple and 2 meat probe ja ks. No more wired cat5 Jack's to worry about failing
 
The RDTC board works great, very robust.... You can also cut away the plastic on a regular cat5 jack and solder the wires directly to the knives that you punch the wires down into, I did that to a few RD's in the early days. Or since it seemed to work for you for a couple years you could just trim back some wire and punch down to a new CAT5 jack, should last a couple more years I would guess....
 
I got things working again. It turned out my ground wire connection was loose and not making a good connection. I fixed that up and things are looking good again. We're about 3 weeks away from having our 2nd kid, so I don't have time for projects right now. Some day though I would like one of those RDTC boards.
 
Glad you got it working again. I purposely chose the ground pin location to be on the end of the CAT5 connector so you can easily cut away the plastic and solder the wires to the post there. Since there are two wires on the ground pin, most likely of different gauges, the ground pin is the most likely pin to give you problems.
 
I actually don't have it totally working. I thought based on the loose ground connection that was for sure the solution. And it may have been part of it. But my servo is still not functioning right, and I'm at a loss as to what's happening. I'm getting 4.96volts on the 5 volt line, and getting 4.6 volts on the servo signal line. This doesn't seem right, I thought the servo signal voltage would be in the microvolt range. I tested voltages with the pit probe connected and the temp set to a setting that would run the fan 100% and open the servo all the way. I'm getting nothing from my servo, no hum or movement at all. And I've even tried another servo, so I don't think it is that. I'm worried I somehow got some errant voltage into my signal line.
 
Can anyone offer any further assistance on getting my servo motor working again? I tried another power supply and seem to be getting the same voltages. With the temp set to 400 and my pit probe laying out on the table, I hooked up my heatermeter and I'm getting 4.96v on the +5v pin, 4.6v or so on the servo signal pin, and 10.3 volts on the blower pin. I assume the voltage drop on the blower pin is due to the fan actually running, because it works as it should. But my servo does not budge, makes no noise at all when power comes on. And replacing it with another servo out of my original 5 pack gave me the same results (ie no indication of life). It seems to me like the problem is inside my heatermeter, but I'm not sure where.

Any pointers on where to look next are appreciated. To be clear, I've been measuring voltages on the solder pins for the CAT5 connecter on the heatermeter board. But I get the same voltages at the servo on the other side of the CAT5 jack and all through my Ethernet cable.
 
The Servo circuit isn't really a circuit, in fact, the SERVO pin used to connect directly to pin 14 on the HM, add 5V and gnd and that's the servo "circuit". Recently a BS170 (Q5) has been added as a servo booster, but it only connects to 3.3v, so even if it is shorted out you wouldn't get near 5v. The ATmega also runs on 3.3v, so I suspect you have something bad in your wiring or CAT5 cable or jack.

I would disconnect the CAT5 cable from your HM and measure those voltages directly on the HM board, do you get the same result? If the voltage on the servo pin drops to normal then plug in your CAT5 cable (only) and measure again. If 5V is back on the SERVO pin then you have a short in the cable, if not then you have a wiring or CAT5 jack problem in your RD. If you have that issue in your RD, and have had it for a few years now, I would just go buy a new CAT5 jack for $2 and cut this one out and put in a new one.....
 
If you do replace the CAT5 Jack, I'd go ahead and throw in an electrolytic capacitor across the servo power as well. It cleans up the signal a bit and allows for smoother operation. A 22 or 47uF 10V should do the trick.
 
Thanks so much for that detailed how to Ralph. It helped me figure out I had a short somewhere in my servo. I removed everything and the signal line went to around 150microvolts on the board. I added the Cat5 cable and it stayed. Finally figured out that all was fine when the servo signal or the 5 volt wire were disconnected. I'm guessing it was in one of the wires leading to the motor, but I couldn't see any breaks in the line, and I didn't feel like messing with finding it when I had 2 brand new spare servos still in my supply drawer. Connected the new one up and it works just fine.

I do think I'll add that capacitor WBegg. I've seen that posted in another thread and was going to use that. But figured I needed to fix this problem first. And now that I've got it fixed, perhaps I'll do that.

Thanks all! Now I can happily BBQ on this 3 day weekend.
 
If you do replace the CAT5 Jack, I'd go ahead and throw in an electrolytic capacitor across the servo power as well. It cleans up the signal a bit and allows for smoother operation. A 22 or 47uF 10V should do the trick.

Regarding this, I found a 25v 47uF electrolytic capacitor in my part drawer. That should work right? The higher voltage just means it can handle 25 vs 10 volts, but the capacitance is the same...so I'm thinking I should be good. Just wanted to hear that from some of you guys that understand electronics better than I do, but I'm fairly certain my thinking is correct here.
 
Yes, you are understanding capacitors correctly, the capacitance value needs match required value, the voltage just needs to be above the operation voltage. You can use a 25V in place of a 10v, however, (physical) size sometimes becomes an issue if you up the voltage.
Since this is an electrolytic capacitor make sure you connect the leg marked (-) to gnd.
 
Glad you got it working...
Yesterday my main HM flaked out somewhat, not connecting to my wifi, looking kinda like a dead rPi but haven't done enough testing to be sure. I threw a spare rPi Zero-W in there and got back up and running. As a result I pulled my RD3 in to calibrate it, other than being a bit smokey and faded from UV exposure it was in surprisingly good shape for being out in the elements for 2 years. Right back out it goes, big grilling weekend, no rest for the workhorse!
 
Mine is out on my covered patio/porch all the time attached to my Green Egg. It is smokey but not really faded. The biggest sign of wear is the rusted screw holding in the servo wing. But I am impressed at its ability to withstand the elements.
 
Ya'll are braver than I am. My server & damper assemblies, along with the HeaterMeter, live indoors unless they're in use. Minnesota weather can be just a tad unpleasant. What are your assemblies printed out of?
 
I leave my RD3 on my grill 24/7/365 in cold chicagoland winters, directly exposed to rain, snow, ice, UV, the works. I Keep it powered on all the time (via CAT5 cable to the HM unit inside the house), a torture test of sorts. I've been surprised myself how resilient it has been, I've had to crack ice on it a couple times to get it to move, it just keeps on chuggin' along! It's been so reliable that I hardly pay attention to it, didn't notice how faded and smokey it was until I had to calibrate it after my rPi died.
 
I'd be somewhat concerned about the blower motor corroding over. The RC servo should be a little more sealed. I hadn't contemplated the possibility of leaving the HM inside.....
 

 

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