Hi guys.
The servo motor on my h2d that controls the flap/door behind the carbon filter has died i believe.
It looks like a standard 9g servo motor, however I’ve tried other non bambu ones and not working. Also tried the one bambu sells for models. I don’t know if the wiring is different to the one they use on the h2d as its certainly not working:)
Bambu support are not the quickest to help so hoping someone has replaced theres maybe ? Or has a greater understsnding of these motors than me. As far as i can tell they can’t just be tested like a normal motor, ie attach power and round it goes. So even with my voltmeter in hand I’m struggling.
Ideally i want to just buy the replacement part. With the correct wires and plug and awsy i go. Cannot see it as a replacement part on site though.
I don’t know anything about the H2D’s design, but I do know a lot about servos since I’ve been using them in RC models for many, many decades.
Some servos need 5V PWM, others will work on 3.3V. Odds are you need one that will work with 3.3V. If your servo is one that’s expecting a 5V signal on the PWM input, it might not work.
Assuming BBL didn’t do something annoying like change the wire order going to the servo, you have two choices for how the 3 wire cable can safely connect. The center wire should always be V+, one of the outer wires is ground and the other is the PWM signal that controls the servo. You can connect the servo “backwards” without damage (the PWM signal going to the GND input and the GND signal going to the PWM input). So if it didn’t work the way you connected it, try reversing the connection of the two outer wires in the 3 wire cable.
Ideally, you could “buzz out” the cable to make certain V+ is on the center lead.
It’s possible the problem is the circuit that drives the servo, and not the servo itself. You can buy a “servo tester” off Amazon for less than $10, which you can then use to test your servo (the old one that might be busted) to eliminate (or confirm) this possibility. If the servo works on the tester, it’s the board that drives the servo in the printer that’s busted, not the servo.
Could probably use any servo, if you also use an adjustable bec like the one castle creations makes. It would have to tap in to a dc power source that was a higher voltage than the servo. I think the bec 2.0 can accept up to 50ish volts and send between 4 and 12 @ up to 15 amps. Cant remember what v1 can do, but its half the price of v2
A buck converter can do the same sort of thing with more limitations.
I agree with @RocketSled though. Its probably not the servo, if youve tried multiple already. Even if voltage was off, it should still spin, just slower or faster than expected and possibly backwards(depending on wiring order). Volts × motor KV rating = rpm
Sorry, I may not have been completely clear… the servo will accept 5V power. Other than servos specifically designed to operate on a lower voltage (they won’t generally be as big as the one in the H2D), they all work on 5V (or more, there are “High Voltage” servos that work on as much as 8.4V).
But older servos need to see a 5V signal on the PWM input. Newer servos will generally work with 3.3V on the PWM input. But they still take 5V for the power input. You can buy “level converters” for this, but a servo that didn’t need it would be more optimal. And small servos are cheap.
I’d be surprised if BBL used a low voltage servo, since the only reason they exist is for very lightweight model aircraft. And I’d be surprised if they used a HV servo because the only advantage they have over 5V is speed, and this flap thing the H2D servo controls doesn’t need to move very fast.
Given this is a mass-marketed consumer appliance, if I was them, I would not have selected anything “special” for this servo. Hobby servos are cheap and very dependable. The use case for this one isn’t very demanding. Why spend money on a part that costs more because it’s customized, when you don’t need customization?