Transmitter controlled 8 servo Quadruped


I would like to build the 8 servo quadruped shown in the link below......

Or this one

Besides chassis parts and the servos, I have no idea what to buy to get this project moving. I was hoping someone could help me find the right components to make my new RC pet walk.

I'm such a beginner in the arduino world but to make my motors turn I use a Arduino Yun + a Adafruit MotorShield V2. BTW I might be wrong but at least it will get you going.

Hope it get you going


Ok I bought this controller set...

I was looking at hex kits and saw that the more pricier ones with servos included this set and they claimed all you need is a battery.

I don't mind buying a motor shield if needed but can you explain a lil of what these two do in conjunction with them selves?

Yeah, it looks kind of cool, but the problem with walkers is they have to hold "themselves" up, as well as carry the weight of the controllers and batteries, unless you want to have trailing wires.

9g micro servos have only 15 oz-in torque, which is just 1/3 of that of the "standard" servos.

People I know who have tried building walkers using micro servos have found the servo torque isn't high enough, so don't be too surprised if you have problems. I've found that many of these ebay thingmabobs, especially from china, look nice, but haven't been tested very well, and don't work very well. Would be nice if you had a youtube video of the walker walking to look at.

With a hexapod, you can get away with slamming the legs at full-speed, but with a quadruped, you definitely need finer control over leg movement speeds, so having a controller that has speed control is a good idea. It's not clear if the one you bought allows you to do this, eg see the following for info on speed control:

Also, in general, I've found that 4-6 NiMH AA-cells in series work good for both regular motorized and walking robots. These have 2000-2500 mA-hr ratings. With 6-cells, you can probably power both the controller and the servos from the same battery, provided you add a lot of capacitors for noise filtering on the power busses.

I actually bought the upgraded higher torque tower pro SG92R found here......

Says torque is at 30 oz.

Hmmmm I know lil to nothing about that board other than its arduino compatible. Also I was told to use 1S battery and I have them in many different capacities. I might end up going ahead though and getting the hex frame and 6 more servos.

Could you point me to the Programming language or what ever I need to learn or to program my new pet?

You should not start threads on the same topic, in 2 different sections of this forum.

Looking around youtube at some of the videos on 9g servo walkers, I see they probably aren't using controlled servo-speeds, just whamming the servos over to their target positions. That's probably ok, given the leg design.

Even with what appears to be "extra" torque servos, you'll likely still have a weight-vs-torque issue, so you cannot pile on too much stuff. However, the way they've designed those hip joints [ie, rotating on a vertical-axis], most of the force is held by the servo mechanical joints, and not by the servo torque itself, so you'll probably get away with it, as long as you go with the 2-DOF legs, and [u]not[/u] try to implement 3-DOF legs, as mentioned in the other thread.

The original photo appears to show them using an Arduino ProMini, and that will probably be ok for totally controlling this thing. You can use the Rduino Servo library.

As I have it, a 1S Lipo battery only provides 3.7V, and that's probably not enough for the servos, which typically specify 4.8V [u]minimum[/u]. So, you'll probably want to go with 4 AA or AAA cells in series [the AAs may be too heavy], and get the 3.3V version of the ProMini or whichever controller you end up using. You can buy ProMini knockoffs for about $3 on ebay.

Also, in general, it's easier to build a Hexapod as the first walker, rather than a Quad, as 6 legs are more stable and you have 50% more torque, and the gait is trivial. Just stay with 2-DOF legs for a starter.

Sorry about the two topics, we will switch to this one.

I was hoping to use the controller kit I bought but if that doesn't work I can buy what ever is needed.

Ok would a 4.8v Lipo Reciever battery do? They are quite light weight and small.

I hear you on the hex. Everyone says the same. I might just go ahead wait on building the quad and get the "same" as a hex kit and 6 more servos.

Ok I was told I needed to learn C++ so I've started learning that. i also need to learn Arduino code. Also the only Arduino coding I've done was define parameters for a quad sketch. Do any of you know of any tutorials that Newbs and laymen can understand to teach me Arduino robotics code?

In general, servo controllers are made to do dedicated servo timing and to be commanded by a "host" processor like an Arduino board, and not do everything else the robot software needs to do, and are not generally programmable. Not sure about the controller you bought. However, as mentioned a $3 ProMini from ebay will directly command all the servos.

I don't know about 4.8V Lipo batteries, I thought they were mainly 3.7V, 7.4V, etc. Got a link?

... teach me Arduino robotics code

I don't think this exists. However, you can find lots of tutorials on the web on general C programming. You need to learn how to program in general first, then start using the servo library, and go from there. You might find walker code on places like Instructables if you hunt around.

Also, you will want to concentrate on learning "C", and not C++ per se. First off, probably 90% of C++ program code is just straight C, and in the Arduino environment, it's probably 98%. Mainly you only see C++ code used in the Libraries, and generally you don't need to reverse-engineer them, just learn the basics [trivial] of how to access them. So start with learning straight C, and then pick up whatever C++ you need as you go along. Otherwise, you'll be buried in obtuse complex nomenclature, which will be overwhelming if all attempted at the same time.

Ok we seriously need to talk about power needs. As mentioned above the TP SG-92R servos operate a 4.8v and can take up to 6v. Non-reachargeables are out. I can't afford to buy batteries every time I want to use it so we need to think about Lipo.

Also I asked the dealer of my Quad who also sells the Hex version using the same type parts says to use a 7.4v along with all the hexes running 9g servos. They also come with the same controller board and wireless TX/RX system.

The controllers input voltage can range from 6.5v~12v or 3.5v~5.5v

It also says... Servos power supply DC generally 5v.

Now this made me think....

Does or can the controller put out the right voltage by either programming or some other means? Like a built in step down circuit?

Can I use a step down circuit inbetween the controllers power input and my battery?

Those schemes are possible. However ,you can likely get away with 4 or 5 NiMH AA- or AAA-cells wired in series to power both servos and controller. Just use the 3.3V ProMini or similar controller, and put some extra capacitor filtering on the power buss [Vin]. It works for me.

But can the out put V of the board to the servos can be regulated and changed?

Ok been doing some research on my SC and ran across this diagram......

As you can see it has a baby blue screw head that looks like the kind that old HIFI's have to secure stereo wires. Labeled Chip VCC---ground---Servo VCC. I'm assuming that these are power inputs.

Here's my idea. Go ahead and buy a few step downs and solder one to my battery so it puts out 5-6v then hook those leads to the Chip VCC and ground, then run a jump wire from the Chip VCC to the Servo VCC.

Should work. Just try it. As an added measure, put a 100-220 uF cap in parallel with a 100 nF cap between the Servo Vcc pin and Gnd.

Ok I decided since everyone keeps telling me that hex's are easier that I would go ahead and do a hex. I'm using the leg parts and clamps from this hex.........

And used this hex as a shopping list.

Now there is a plastic spider hex around $100 that comes with everything you need but I'm a lil confused about the amperage considerations. This kit for the SG-90 plastic kit says to use a 25amp rectifier bridge as voltage regulator.

The one in the second link shows a bigger bot using bigger servos and it uses a 12A step down power module. Which would be correct for my hex?

I also bought the Nano v3.0 and the nano terminal shield. Can you think of anything else I need to order?

Now Im also designing my own spider platform for the Hex to attach the legs too. I plan to attach the servos to the platform using servo horns. Then using the servo clamps from the other hex to clamp two servos together like I'm seeing on the other hexes where one servo arm is at top and one on the side and square.

Also I want to point out that the servo controller "CAN" be used by itself. There are drivers and a program called Torobot rios_usc that will allow you import arduino code (with a few alterations) to the program to control it either via rios_usc or download it and control it through the Wireless PS2 type controller. It just has to be written using your notepad. There is a seperate topic for the Torobot program, I did this document how to control the board through that program. Im still trying to figure it out but I have run some arduino through it and once I got the syntax right it executes the code. Other wise I'm using the arduino controllers added to the servo controller to program it.