Well, I’ve done some projects with robotics and other electronics but have not used servos for anything before and I guess I let my wallet push me to get underpowered servos. I bought 32 HS-475HB servos to build a full biped but after reading some posts, I should have gone with something stronger. Hmm.
~Mike
For I biped with 32 servos you would probably want something a little stronger. You don’t really know untill you build the robot how much power it will really need. But more power is always better.
You can maybe return them, because 76 oz./in. wont get you far… you can build a BRAT, taht’s it about
Sam
I was planning on building a full humanoid type but with reversed knees. 6 DOF on each limb. Yes, I will start small and build up to the big one so i guess i can wait and get stronger servos when I need them for strength.
~Mike
ok, because for a full humanoid with 22 servos like the biped pete or nick, you need minimum 5645’s (168 oz./in.).
Would I need 5645’s on both arms and legs or just legs? I guess it depends on the size/weight of the arms. I’m planning on making the arm pictured on lynxmotions page that has the ‘hand’ but with an extra joint in the arm.
~Mike
it always depends on what you want to use it for. you can probably go with the 133 oz./in. for the amrs if you don’t want to lift anything heavy with them, lower would probably become jiterry (mmm, how do you write that?).
Jittery.
LOL well, i was close
I put in my bracket order two days ago and it’s still Pending. Any idea when that’ll go through. The place is only 4 hours away so once it ships, it’ll probably be here the next day.
~Mike
Orders can still say Pending even after you have received it. Don’t worry because you will get your stuff as soon as Lynxmotion can get it shipped which is typically 3 - 5 days for US shipments. Well, that’s how long it usually takes to get stuff I order, but your milage may vary. 
I am not connected with Lynxmotion, except as a very satisfied customer and continuing customer. 
8-Dale
After building a handfull of humanoid robots, you will want to have every servo in the robot to have the same torque rating. Bipeds fall down. There is nothing you can do to prevent that from happening. After a while, you are going to want to program the robot to get on its feet on its own. If your arm servos are too weak, it won’t be able to get up. If you compare the price difference in using cheaper servos in the arms to the over all costs of the robot, to using good servos in the arms, the overall cost difference is small. Much smaller than having to buy new servos later to replace them.
The only exception to this would be the head servo.
Pete
Well, I’m going to buy a couple dozen 5955’s to replace the servos i got. I was about to make that purchase until last weekend i noticed a flat tire on my car and the machanic told me all four tires had bad sidewall damage. Time for new tires($400)…not to mention auto insurance ($700). So i guess I’ll have to wait a few weeks till i get a couple more paychecks in the bank.
~Mike
I don’t agree here. I don’t think it’s necessary to have all servos have the same torque ratings. Servos should be chosen for each joint according to how much of a load is going to be handled. For instance, I wouldn’t use an HS-5955TG unless I really needed one at a particular joint, because these are very expensive servos.
I’d use HS-5645MG servos everywhere except in cases of extreme loads, such as the ankles and hip vertical joints where these have to support the the entire robot, for instance. I’d use an HS-5955TG at the ankle and hip vertical for sure.
Neither of the biped projects I am working on now have arms, but I am allowing connections if I want to attach arms later.
I still say it depends on how much of a load the servo is going to have to handle. If the servos are placed intelligently, there should not be any problems. Considering the HS-5645MG at $54.95 and the HS-5955TG at $114.95, I’d say that is quite a difference in price. There is no way I am using an HS-5955TG unless it is absolutely necessary because of extreme load.
8-Dale
My point is when choosing servos, try to imagine everything you might want the robot to do. Like walk, bend over, squat up and down, stand up. Then for the more challenging tasks, walking up and down stairs, or holding one leg out front and squatting.
These different activities have different load demands on the servos. Walking on a flat smooth surface or standing still are the easiest things to have the robot do. Squatting has a lot more demands on the thigh, calf, and foot servos. Ankle servos are not used as much since both feet are on the ground.
Then when you get to having the robot walk up some stairs. Much more demands on all of the leg servos for one leg. Not only is the one leg trying to move the robot forward, and balance, it has to dynamically lift the entire weight of the robot.
Then lets look at costs the cost risks. If your robot has 10 servos for the legs, and you want to use the HS-5955TG for the hips and ankles (4 total) and the HS-5645MG servos for the other 6 servos you would spend $459.80 for the HS-5955TG servos and $329.70 for the HS-5645MG servos. Total $789.50 Then after you build the robot, get it up and running, and then start having it do some of the more difficult activities and learn that the HS-5645MG servos don’t have the power to do all the things you want the robot to do, then you end up getting 6 more HS-5955TG servos and spend another $689.70. In the end, you spent $329.70 more than you needed to spend.
Sometimes you don’t have the budget to spend all this at one time. so you go with the two servo size route and when you have the extra funds, get the better servos.
Believe me, the more power you have up front, the better off you have because you limit what you can do to compensate for lower powered servos.
This is an expensive hobby.
Pete
I have been considering what activities my robots would be doing as I choose servos for them. However, I don’t need to consider some activities right away. I don’t necessarily want the robots to be able to do every type of action. The legs on my bipeds are hybrid designs, and allow some things to be done easier and with less power required than might be needed with a standard design. The BiPod has 4DOF hybrid legs and Mega Scout has 8DOF hybrid legs.
Even if I did go this route and end up having to upgrade one or more joints at some point, I wouldn’t look at it like I had spent more than I needed to. There are always other projects to use servos on. I already have three custom robot designs, one of which I am building right now - The BiPod. I won’t be using standard servos if my experimentation with Open Servo project works out as I hope.
I could buy maybe two HS-5645MG servos per month (possibly three), or one HS-5955TG per month. However, for the first two servos I get for The BiPod, I am getting two HS-645MG servos and having them made into Open Servos. This should get me a servo at least as good as an HS-5645MG as far as the torque rating, and it will be much more flexible and accessible. The HS-645MG has the same components as the HS-5645MG, except for the electronics.
Yes, it is an expensive hobby. However, it is possible to do quite a lot on a limited budget. I have learned so much about robots and robotics just tinkering with WALTER, it is really amazing. I’ve learned how to work with several different kinds of sensors, experimented with different configurations of sensors, including two different designs of pan/tilt turrets, etc. WALTER is an excellent experimental platform. I am just starting into the custom designing with The BiPod, and I believe I have figured out how it can walk in both modes now. It is going to be interesting, to be sure.
8-Dale
I’ve decided to wait a little longer. I need to learn this software and get something simple walking. I’m also planning to get a PIC controller but i think I’ll wait till the “new version” comes out that is in the works.
Hopefully I will get the raise I was promised next month and will have more money coming in.
Now…where can i find some more of this Spare Timeâ„¢ stuff?
~Mike
What “new version” PIC controller are you referring to?
8-Dale
Could be the Explorer 16 system
microchip.com/stellent/idcpl … e=en024858
I’m holding back from it at the moment to see how others get on with it.
Sorry, I meant the future Bot Board being discussed the the Bot Board section.
I may even build my own, I have experience with Atmel chips.