Resolved by CardboardHacker!
Hi there.
My name is Steve and I am new to the forum so I would like to say hi to everyone. I do have a question I hope someone can help me with regarding my current robot build so I hope this is the right place to ask. I am in the middle of building my own version of a full size K-9 with a few differences that I will put up on the EZ Robots showcase pages when he is completed. I am currently waiting for my EZ goodies to arrive which are due sometime this month (June, 14) and so far I have pretty much completed his body and rolling chassis.
The question I want to pose has to do with the rolling chassis/drivetrain. The parts for the chassis have mainly come from a kiddies ride on car which has two 12v, 30w drive motors which produce two fixed forward and reverse speeds (slow 3MPH and fast 5MPH) and a single speed 12v steering motor, connected to a control/radio control receiver box, controlled by a R/C controller and powered by a 12v 7Ah rechargeable battery. The R/C controller will be located inside the body and 2 servos via the EZ-B will move the joysticks for the movement (one servo for forward and reverse, and the other for left and right).
I have this pretty much sorted, but hear is where I need the help confused. . I want to slow all 3 motors down a bit. I would like to have the steering motor turn slower so there is more precise movement via the servo control, and would like to be able to adjust the speed of the drive motors so I can have a slower, almost a crawl, speed while K-9 is roaming the house, and then be able to readjust the speed so he can move quicker around larger area or open spaces. The current "slow" speed is about 3 MPH but it is just a bit to quick to navigate autonomously around my house so I'm looking for a hopefully simple solution.
I had an idea of simply splicing through one of the motor wires on each motor and wiring in a 12v potentiometer which I could attach to his control panel and adjust it/them as needed (or even servo controlled, but first things first). Could it be as simple as that or would I need something more? I have also read online about maybe using a PWM but I wouldn't know how to wire it (or them as the case maybe) up. Would using a PWM do what I'm looking to do and would it even work on the set up I have?
I am not really experienced in using or installing resistors or soldering circuit boards ect so a simple "easy for me to do" solution would be great, so any help and advice or solutions anybody here can offer really would be appreciated, and thanks in advance 
.
Steve
Thanks for that Rich. I would like to air on the side of caution and leave a little safety margin. Yes the surges are very quick, less than 1/2 a second so it all sounds good.
Having never used EZ Robots equipment before I didn't realise that you could connect two L298n motor controllers in to one EZ-B so that certainly does sound like the way to go.
Thanks again buddy.
Steve.
Yeah, running two isn't something that's done often but it's pretty simple to do. The main issue is the number of digital ports two will take up, however if you only use 1 channel on the steering one then you can cut the ports used down by 3.
Basically, it takes 2 digital ports to tell a H-Bridge to move a motor. My tutorial that Dave linked to explains it all in the truth tables but to be honest, this sounds like a fun little project to work on so I may wind up knocking up an Example Project for this scenario later
Sorry Rich, just to clarify, when you say digital ports, are these the same ports the servos plug in to? Still waiting for my EZ goodies to arrive so I'm only going by photos and what I have read so far.
I did have a quick look at your tutorial the other day but didn't quite take it all in. Will deffo have another look.
And thanks for the welcome.
Steve.
Yes that's correct, digital ports are where the servos plug in.
Each digital port has a ground, Vcc and Signal pin. The signal pins are what basically control things through various methods such as "highs and lows", "PWM" and Serial communication. As crazy at it now sounds to me, I have always expected people to just know what digital ports are, what highs and lows are, what PWM is etc. yet I should know better since I came here with no knowledge of anything to do with microcontrollers, no idea what a digital high was (I thought it was something you get from watching an awesome 3d movie) or what PWM is.
When you have time have a read through the Learn section of the site and check out each of the tutorial pages (open ARC, add a control and click on the ?). This should help you learn and understand what everything does and how everything works.
Nice one, thanks for that. This sure is a learning curve for me but enjoying it never the less. Hey, I know what a PWM is already so that's a start
Seriously though, I'm good with all the practical side of things, always have been ever since I was old enough to hold a screwdriver (the right way up), but it's the terminology and technical theory I'm still trips me up from time to time and using micro controllers really is a first for me, but thanks to people like yourself, you all make it that little bit easier.
Anyway back to the matter at hand, I don't really have a problem loosing a few digital ports. My original idea that I mentioned at the start of this thread was to have 2 servos moving joysticks on a radio controller, but now with the motor controller idea, that will be 2 less servos I will be using so I will have plenty of room to connect two motor controllers so just added 2 controllers to my order.
I will have another look at your tutorial and when the goodies arrive, sometime this month I hope, I may check back with you Rich, about scripting the 2 controllers if I get stuck.
Thanks again for the advice yourself and everybody else here has offered up and I look forward to sharing my little project soon.
Steve.
:)
Just wanted to say that I have ordered two 2.5 motor controllers so I'll let you know how I get on.
Steve.
I have another question I would like to ask regarding using two 2.5 amp motor controllers through one EZ-B, but I am going to start another thread as my original question about reducing the speed of my 12v motors has now been answered and this is going slightly off subject. Another thread asking about this may also help other people who may need help and may be easier to find.
I'm going to close this now but as I can only select one member to "Thank" resolving this question who will be Technopro as he was the first one who answered my initial question, but I also wanted to thank everybody who replied as you were all very helpful, especially Rich for his suggestions and who helped make things a little easier to understand.
All the best and thanks again.
Steve.
:)
Steve- I am glad you came to the forum! Looks like you got quite a bit of info!