HK-5320 servo dosent like the standard servo paramiters

I am converting a couple of dual needle brake pressure gauges from air to servo operation,

So i needed the smallest servo's i could get, and the HK-5320's are perfect, absolutely tiny things they are,

As i work out the linkage and positions inside the gauge, i have my uno running the servo sweep sketch,

However the HK-5320's are running hot, buzzing a bit and not giving me full sweep.

I've seen someone on youtube mention he found out the HK-5320's run best on a 16ms pulse or something, and standard arduino servo code is 22ms.

Can someone tell me what i need to do to make my servo's happy?? The servo's will eventually be running on my mega, and moving according to data from a simulator as a varying value from 0 to 1024.

Are you using an external power supply? If so, do you have the servo power supply and arduino grounds connected together?

That servo should work fine with the industry standard 1-2 millisecond pulse width repeated every 20 millisecond, as the arduino servo library uses. I too suspect servo power problems. As a good test use 4 series connected AA cells to power just the servos with a ground wire added between the AA battery pack negative terminal and an arduino ground pin. If that works OK then you will have to come up with a independent 4.8 to 6.0 VDC voltage source to power the servos rather then trying to power them from the arduino 5V pin. This is a very common problem people have when attempting to power servos directly from an arduino board. An arduino is great for controlling servos, not so good at powering them.

Lefty

I'm running the servos at exactly 4.8 volts from my bench psu, they consume very very low currents as expected as they are really tiny servo's, they run a little faster at 6 volts, but i don't want to burn them out as they get hot enough at 4.8 volts,

And yup i have the grounds connected between the psu and arduino,

There are a few references on the web about these particular servo's not liking the standard servo library settings, and most mention 16ms is the sweet spot for these, but i'm not sure how to implement that, not even 100% sure if it is milliseconds or microseconds, as the positioning part is done in microseconds.

My experience with the small 9g servos with a poor ground resulted in them behaving eratically and getting hot. Servos should not get hot when not moving or under load. Your operation at the minimum 4.8v might add issues.

There are a few references on the web about these particular servo's not liking the standard servo library settings, and most mention 16ms is the sweet spot for these, but i'm not sure how to implement that, not even 100% sure if it is milliseconds or microseconds, as the positioning part is done in microseconds.

Well if you read it on the web it must be true. ;)

Bottom line if a standard hobby R/C servo can't work well at the standard R/C format of 1-2millisec pulses repeated every 20-25 millisec then there is something terribly wrong with it, as that is the industry standard for controlling servo devices. It's true that some servos can be made to work at a faster refresh rate but again if a 200 mph Ferrari can't also drive well at 60 mph then there is something wrong with it.

Lefty

oh they don't get hot when not moving, and they are only pulling a quadrant gear to move the needle on a gauge, so a very small load,

it's just when they are running on the sweep pattern, they get hot,

i know servo's should all run on around 20ms, but apparently these run much better on 16ms,

i imagine that they would be absolutely fine, as they won't be sweeping across the dial all the time when in use, one will be slowly moved to a certain position, then will vary slowly to represent air tank pressure, the other will move fast to positions varying on brake chamber pressure indicated, then go back to zero position and stay there most of the time,

Just they are fitted inside an automotive gauge, which requires the bezel prizing off to gain access, so i'd really rather not have to open it up again in a few weeks time to replace a burn out servo if i can avoid it by changing a few parameters of the library now.

if it matters, these are 1.7g servo's, about the smallest rotary servo's you can get, i did try those featherlight linear servo's, but they were naff, lots of backlash due to the way the screw thread is mounted to move the horn along the linear pot,

Just found out these servo's are actually rated for 2.8 to 4.2 volts, so i've been over volting them a little rather than under volting them,

They come with a micro JST connector fitted, so are designed to plug into those feather light RX boards for indoor planes or small helicopters, which usually run on a single cell LiPo, and hence they 'could' have a different pulse requirment to normal servo's?

Also they have a 140 degree motion, but move 90 degrees on the 1 to 2ms pulses, needing 0.8 to 2.2ms to get max rotation.

i know servo's should all run on around 20ms, but apparently these run much better on 16ms,

I've read what you say you heard. I just don't believe it to be factual. In my opinion it's just yet another web myth that someone posted to try and impress someone else. If that servo can work well at 16 ms refresh rate it should work even better at 20 msec, not the other way around. But one would have to understand the underlining circuitry inside a servo to make sense of what is being said.

Lefty

gazz: Just found out these servo's are actually rated for 2.8 to 4.2 volts, so i've been over volting them a little rather than under volting them,

They come with a micro JST connector fitted, so are designed to plug into those feather light RX boards for indoor planes or small helicopters, which usually run on a single cell LiPo, and hence they 'could' have a different pulse requirment to normal servo's?

I stand by my statements, over voltage may be a problem for your servos, but using a 20 millsec refresh rate is not a problem or the reason you are having 'symptoms'.

Lefty