I was pondering the same with my Hearoid build, trying to replace the DC motors for modified servos, but space was an issue and I was unsure if the servos would be up to the task.

I opted to change my plan and reuse the DC motors. If it's not broke don't fix it and all that. A H-Bridge is required to drive the motors and uses up 4 ports on the EZ-B. It might be worth looking in to.

The H-Bridge I plan to use is the TB6612FNG. It does require some soldering though. Soldering aside, the H-Bridge option seems the most simple.

There is also the 2.5 Amp Motor Controller available in the EZ-Robot store which should run the DC motors. DJ has videos showing both controllers and how to wire them if they are of interest to you.

I don't think you'd be happy with the speed of the modified servos. Also, that weight might be an issue. Larger wheels will help with torque, but you will sacrifice speed.

Our hbridge is real easy to setup I know it's a tiny bit more effort, but it'll be worth it

Guess that's the route I will take then. I had ordered the motor controller with my kit just in case, so I'll have everything I need anyways. The servo route was appealing since everything was self contained. Gotta find a place to store the controller board now, and plan for alot more wire management. The schematic for the motor controller shows sharing the same power source, but there shouldn't be a problem supplying a separate power source for just the motors? Don't want to overlook something.

Also just saw the telnet server feature, which really excites me since it opens up more options for control. Not reliant on VB or C#, just send telnet commands via any language on any number of devices. Android program that interfaces just the way I want it to for example. But that's off topic.

@GIjim Separate power will work fine, just keep a common ground between the two power sources, EZ-B and H-Bridge. That said, you can use up to 17v DC to power your EZ-B (it has internal power regulators) so you could simply run everything off a single power source like a 12v battery.

Speaking of common ground, the tutorial video and schematic differ slightly, in that the schematic shows ground running to the battery negative. In the video, DJ runs ground from the EZ-B, with a single positive wire as the only thing going from battery to motor controller. Obviously, that method works and I'm guessing it doesn't really matter either way.

Jim

@GIjim I don't recall the video you are referring too, but what you describe is that the ground path from the H-Bridge back to the battery was running through the EZ-B's own ground plane... not generally an issue with the lower currents we usually run with toy motors. EDIT I found the video... no change in my following recommendation.

I would suggest having the common point of grounding be at the batteries themselves (the negative terminals) or preferably at a ground breakout strip.

By keeping discrete wiring paths also means you can use differing gauges of wiring for the motors and controller (as required based on amperage) then what is required for the EZ-B, even if sharing the same power source.

Also, the 5v line running from the EZ-B digital port to the 5v input on the H-Bridge is optional. If you leave it out, then you can use the little switch on the h-bridge to turn it on and off (it will draw its power from the motor supply). I use it this way to keep my Gunnerator from accidentally driving off the bench when I am testing controls

For sure consider I would use original gearbox in many cases. Even if motors are bad, most toy motors are a standard sizes based on Mabuchi motors. This is the most popular name i see and can cross reference motor casings and voltage to match your robots needs. What vintage robot are you planning on modding? I wanted to say welcome to the EZ Robot community and we look forward to seeing your projects grow! - Josh S