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Asked — Edited

H-Bridge -- How To Allow The Chassis To Turn

Hello,

I have a simple 4wd chasis from sainsmart, using EZB and 2.5 amp Hbrige. I cannot make it to turn (wood floor). The only way I got the platform to run is by stripping out the rubbers on rear wheels so there's less friction and it can turn. It seems that while given the order to turn the Hbridge runs the wheels on both sides at the same speed while the wheels on the inner side should run much slower than the wheels on the outer side, is that correct ? If so, do you know what could possibly allow me to have the wheels to turn slower on one side beside using PWN each time I want to turn ?

Thanks,

Elfege


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#1  
it sounds like you need to adjust your movement panel, you might have you trigger ports mixed up.
which h bridge do you have ? also how are you wiring it... need a little more info please, pics will help;)
#2  
Thank you Derrick for your answer. It's kind of tricky to send pictures because the bridge is inside the chassis.

However it seems I just found a solution : by adding two more powerful motors stripped out from an old broken Rovio (from Wowwee) it now works better.

I guess I have to bring more power to the motors if I want to increase the directional efficiency or install omnidirectional wheels. I've searched online but I know nothing about motors so I don't know what amp and wattage I need...

Here is a link to the documentation, it doesn't give much caracteristics about the motors though :
https://s3-ap-northeast-1.amazonaws.com/sain-amzn/20/20-011-922/4WD.pdf

So, basically, what kind of specs should I look for to have 4 more powerful motors ?

Many thanks,

Elfege
#3  
It seems the motors provided with the platform (I called it chassis, I think it a French word... sorry) are 220rpm so I can just look for higher but I'm kind of lost btween rpm, torque and voltages... there are plenty of different models online. I even see a 5000 rpm at 1.5v, which I guess would burn with my config since Hbridge is linked to main power (8volts li-po)... I guess what I need is torque because it has to overcome the friction induced by the rubbers but I don't want to build a turtle either:)
#4  
it's all really dependent on your build. are you going to add more weight? if so find a motor with more torque.A lot of people on the forum use 6v motors in their builds which seem to do well. I use 1 12v motor at 60 rpm and my bot is really two fast, I have use pwm to pulse the motors speed down. so I would suggest you find a 6v motor with a 100rpm. the slower the rpm the higher the torque." please correct me if i'm wrong"

take a look at this ,"just make sure it will fit"
www.robotshop.com/metal-gearmotor-1576.html
with this motor x 4 you should have 640oz of stall torque to get you moving
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