Reliable Source for MG90S


 

David V

New member
Hey all, new to the community so apologize for this basic question, but I'm having a difficult time finding a reliable source for this servo. I've asked Ralph to print up the RD3 and I think I've picked up everything else I need beside this one.

A quick google search shows some supplies off Amazon, but others have warned of counterfeits which is the same reason I was steering clear of eBay.

Hobby King has one that's advertised as "Turnigy", rather than Tower Pro. AdaFruit has the MG90D rather than MG90S. Bang Good (who the heck is this even) advertises one but some YouTube reviews call them out as counterfeit, so back to square one. Value Hobby and GetFPV are also out of stock, though I've no idea how reputable they are so perhaps that's a good thing. Jsumo is in stock but they ship via registered air or DHL so I suspect that's probably an international shipper which again brings me back to point 1.

I'm sure I'm overthinking this and can probably just pick any old one off eBay, but I have limited electrical knowledge to begin with so anything that reduces the possibility of having to troubleshoot is good by me.

Thoughts, even if it's to tell me I'm overthinking this, are appreciated.
 
It's kindof a crap shoot... Almost every "Tower Pro MG90s" that I have purchased, counterfeit or not, has functioned well enough to do the job. Some work great, others have a little jitter, some move with more authority, but for the most part they work. These servo's are cheap, roll the dice and grab one, if you're not happy with it try another.
As long as those other brand servo's fit into the opening on the RD3 they should work, though I cannot confirm fitment on any of them. I know the sister servo "Tower Pro SG90" does NOT fit, so, another crap shoot on fitment...
 
I know the Hobby King Turnigy branded MG90S is not the same servo measurement wise.

I get mine straight from Tower Pro, but you'll have to send them an e-mail to order, as there is no "cart" item for them on their website. Last time I ordered, I got 20 for $4.20/ea so not sure what price for 1 would be from them.

http://www.towerpro.com.tw/product/mg90s-3/

EDIT: Just found the old invoice. With shipping and "PayPal Fee", my purchase came out to $5.54/ea. i don't think you're going to get a deal from them if you want just one, as these ship from China via DHL.
 
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Thanks both - I was actually thinking about purchasing from Hobby King. Really glad you mentioned something. I didn't even think about ordering from Tower Pro directly. Just assumed they didn't sell directly to consumer anymore. I'll probably pick one or two off eBay/Amazon and hope they work, like Ralph said. If all else fails I'll reach out to Tower Pro directly.
 
Also, i would suggest installing a capacitor (47uF or such) across the servo power. I install mine in the jack itself. It tends to calm down any spastic movements of the servo.

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I have a question with this, I just pinned my MG90 for the barrel servo and it goes nuts when I connect to my HM. If I make both timing settings 0 us then it sits still, but any number above it will chatter and do full 360 degree rotations at various intervals. You think this is a problem the way its connected to the jack or should I meter out the board and make sure my solder work is correct?
 
I would try putting a capacitor across the 5V and GND wires at the servo end like WBegg suggests in the post above yours. Even if you're not using a punchdown jack it can definitely reduce or eliminate the crazy uncontrollable servo effect.
 
Good deal Ill give that a whirl. I used a molex connector to create a pigtail of sorts for grounds of the servo and the fan so I didn't have to punch down two wires into jack . Wonder if that has anything to do with it as well
 
The cap made such a huge difference. I was hesitant but it calmed the servo down incredibly. The only this I am having trouble understanding is when I put the HM into lid mode it wants to do a revolution or two. So I guess my question was is when I am setting up for a cook do I need to set the servo high limit visually so its 100% open and then tailor the low limit to 90 degrees do be closed when in lid mode? Hope that makes a sense.
 
How I set them up initially I set the output so the servo is either at 0% or 100% output, then put the top bit on the damper/servo in either the just barely fully closed or just barely fully open position. Then set the output for the opposite position and adjust the pulse duration for that value until it is just barely fully open or fully closed. It is easiest to switch between the two positions by setting the setpoint to "0%" or "100%" and verifying the opening is where it should be. Going from 1% to 0% output can take up to 10 seconds for the servo to "commit" the output, because HeaterMeter doesn't update the servo position every second for teeny moves since in practice it bounces back and forth 1% in output and this way the servo doesn't have to move back and forth constantly and wear out. I think it has to move 50uS of position before it will force a move, or up to 10 seconds of delay. Going in and out of lid mode works as well from 100% to 0% and back again, but doesn't activate in manual mode.

Setting the servo endpoints forces a move regardless of how small it is though.
 
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6 hours into first test run and going pretty well. Thanks Bryan for the servo advice. That and the servo mode page helped me nail it. Maybe a trivial question but the yellow on the analytics page was very active until I changed my Derivative from 5 to 2. Now temp fluctuates much less than earlier. Is the yellow line a servo position marker? It cooberates with the fan activity so that’s what I am assuming.
 
Great! The little yellow pip is the average PID output over the past... 5 minutes? It's one of those things I thought would be really useful to know back when I first was laying out the webui design, but didn't turn out to be useful at all.

EDIT: It is a 1/240 exponential moving average, so about a 4 minute average.
 
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