I am having a bit of trouble with my hexapod, and I’m hoping some of you guys or girls could help me out,
I made a hexapod with all Hitec HS-311, but I couldn’t get it to stand up and walk. So figured I needed to get some better/stronger servo’s. I went for the Turnigy S-901D. (thinking the problem was with the servo’s). At first replaced all the femurs, it would stand up, but still would drag it’s bottom when walking. So ordered for the tibia’s also the S901D’s.
But now it’s asking to much power from the battery Now I think the problem I am having is a good power supplying the hexapod. The Hitec HS-311 would do just fine on an Nimh 6V 2300mah battery. But I’m guessing the TGY S901D’s ask for a bit more current. Can’t seem to find any datasheet about these. Google just sends me back to HobbyK, where I got them.
mechannically, I have the HS-311 for coxa’s und the rest are S901D’s. About 1,5 kg’s in total. I used the phoenix code on an Arduino Mega with an PS3 controller, and as soon as I start a walking gait(doesn’t matter which one) I see the voltage drop to 4 / 4,5 volts. It draws with about 3amps. But this was with the hex on a fixture. So probably when walking with servo’s under load about double, 6amps max.? The whole starts to behave erratically. From what I read online the SSC-32 resets itself, I can see the blue power led blink, when under a certain voltage. So yeah,…
I can probably power the servo’s with a fresh 6,V nimh battery, but will probably get the same behaviour. When I compare my hex with the phoenix lynxmotion, all the servo’s are powered with a nimh battery. So anybody know what the difference is between the TGY S901D and the Hitec 's HS645? Should I just get a Lipo with voltage regulator, to fix the issue?
I have read about all the issues with lipo’s. If I’m steered towards a Lipo battery i will get a good charger for it, voltage regulator with either a cut-off or a fuse, etc etc.
What are your thoughts on this? am I thinking in the right direction or
Just got all the servo’s in today, and was really excited, hoping to get it to start walking Did not suspect the power supply to be insufficient
Before we start making suggestions, can you provide a few clear photos of your current robot so we can see the frame, the motors and the power, as well as the electronics? When you reply to the message, you will see an “Attachment” section below the reply window.
Hi Coleman!!
Here are a few photo’s from my current hexapod.Hopefully they are not too big. If they are, you may delete them and I will upload smaller ones. (couldn’t find any rules on this)
The measurements are taken at the battery terminals. Left my digital meter at work
The voltage drops below the recommended 5.3 volts the SSC-32U requires. Which in turns resets it and sets the servo back to the position I put in the register with LynxTerm. Which makes them behave erattically. I’m just really wondering if I am in need of an battery that can output a bigger current without the loss of voltage, if so a Lipo with voltage regulator or nimh with voltage regulator.
An arduino mega is running the pheonix code, which in turn is sending the servo commands to an SSC-32U V.2. The mega has an Keyes USB shield for the bluetooth connection for the PS3 controller.
I checked the specs from the nimh battery and it states that the recommended discharge current should be between 230 and 2300mA. So problably it wasn’t going to be sufficient from the start. I put an pdf-datasheet for the battery aswell in the attachments.
ofcourse…!!! Eureka!!
If powered by a 7.2 or higher Lipo or Nimh battery, the voltage is allowed drop because of the current drawn. But because of the voltage regulator it will output a reasonably steady 6volts, with the current asked. At least, as long as the voltage is higher than the voltage regulator output. But by then the battery will be drained and the voltage regulator will cut-off the battery from supplying power, if it goes below.
Be careful about applying more than around 6.6V - the RC servos are really meant to be used at 4.8V to 6V.
The work-around for the voltage drop is to use a separate battery for the logic voltage.
I think, I will power the SSC and mega with the current nihm 6,0 volts. That will do nicely and get a better battery-pack for the servo’s. If i do go with a higher voltage battery, will step-down with 6V 10A voltage regulator for the servo’s. I think (hope) this will do the trick.
The above mentioned theory is correct, right?
I did try the work-around, and power the logic separatly, but don’t have the right power-supply lying around for the servo’s. So that got me nowhere.
Now I think the problem I am having is a good power supplying the hexapod. The Hitec HS-311 would do just fine on an Nimh 6V 2300mah battery. But I’m guessing the TGY S901D’s ask for a bit more current. Can’t seem to find any datasheet about these. Google just sends me back to HobbyK, where I got them.
