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Ireland
Asked — Edited

Robonova Servo

Hi.
I have planned to use ez-b4 for my robonova-1.
It uses Hitec HSR-8498HB servos.
Normal servos turning 0-190 by 1-2ms signal
These servos turning 0-190 by 0.55-2.45ms signal.
So It turns by Ez-b only about +-60 degree.


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So I said i wont let it go.
I downloaded the Hmi servo programmer. In the help section you can see the schematic of the cable. was puting that together in 5 minutes.Very simple.
You can have the hmi programmer from
Hitec HMI servo programmer


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But affortunatelly robonovas servos have 1.08 firmware.
The normal commersial servos have 1.02 software.
1.08 Can be controlled by the software and read but it can not be programmed
1.02 Can be controlled by the software and read and it can be programmed aswell.

At least I could see the servo can turn 180 degree.

Is there any chance to squeeze out 0.55-2.45ms signal from ez-b?
Or just get over the maximum setting of 180 degre in the script?
Or any one have servo with 1.02 firmware?

I would be happy for any solution.

Thanks.

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Ireland
#1  
Hi guys.
If any one interested I solved the problem.
I opened up the servo. There is an 4.7 Kohm potmeter. It is connected for the PCB with 3 wires. The red one goes for the ground.
Disconect the red wire and put an 910 Ohm resistor between the pcb and red wire.

Than your servo is going to be work on the full scale of range by EZ-b.
And the center is going to be on the middle. And you do not need to profile your servo.
Basically plug and play.
Cheers.
Ireland
#2  
I had a problem with the tantalum capacitors aswell.
One of them become shorted. But it could be the ageing aswell.
The earliest owner did not use the robot for while.
Anyway I have ordered new tantalum capacitors 16V.
vishay TR3B336K016C0350 Just couple of euros prevent the problems in the future.
The FET-s are 30V, caps are 16V, I do not know any thing about te 3v stabilizator for atmel mega8 but it should be OK.
The motor is 4.6 ohm.
I=8.2V/4.6Ohm less then 2 amp on full throttle.
The FET-s are 5amp
The power dissipation of the FET 2w (That makes me worry)
P=8.2V x 2Amp 16w
This is the theory based on the resistance of the motor.


I will test the servos in real life for 8.2v. Overheating and current aswell. Because I would like to use 2Slipo battery for it.

Pictures or video later.
I will keep you updated.
PRO
Synthiam
#4  
That's a good idea to add a resistor:) Smart thinking Oaba!
United Kingdom
#5  
Thank you oaba for sharing your findings and schematics!

I have just bought an ez-b v4 to change the controller on my Robonova1 (I was originally using an Arduino but ran out of memory for my control code).
Ireland
#6  
EchoLima If you have any question. Just go on. Might I can help.
United Kingdom
#7  
Thanks oaba, I've just sat down with Hitec HMI servo programmer and unfortunately my servos are firmware 1.08 too.

I actually want to try and avoid altering my servos because I intermittently reconnect MR-C3024 to quickly show off RN1 or to remind myself of the factory movements.

I read from [https://www.ez-robot.com/Tutorials/Hardware.aspx?id=4]

'The EZ-B has timing below 1ms and above 2ms to accommodate all servo types. Some servos do not fall within the specifications and require unusual timing. When testing with your servo, make sure you recognize the max and min values and set them in the control.'

So my plan now is to get ez-b v4 up and running and see what controls are available. DJ Sures - is it possible to alter the pulse output of the ezB? Essentially adding a 'custom' servo to the ezB? I've got my ezB and power cable today so still working through tutorials.

(Input is very welcome if you see me going towards a dead end!)

I'll follow oaba's good example and put any useful developments here for future users.
#8  
Currently no custom timing available. This question seems to be coming up more and more often though, so I would not be surprised to see DJ add it as an advanced feature somewhere down the line. I don't speak for EZ-Robot though, so I could be completely wrong.

Alan