So yes, it’s damn hard and thanks for recommendation, maybe I will have to buy another encoders after all (thought about hall effect sensors but my motors are missing extended shaft to put the magnetic disc on), but for now let’s fight with those I’ve got:)

It is tricky to get these robots to go straight, even with encoders it can be tricky.

I have tried to use the redbot wheel encoder, but I’ve found that it’s not very good. I’m not sure it gets great reflections off the encoder discs and so the one I had seemed to miss pulses fairly regularly… These encoders were also used in a recent robot building MOOC, and the forums suggest that other people had problems…

I would recommend using quadrature encoders which give both the speed and direction of the wheels. We are planning to release some encoders soon, but it’s on hold for a month or two as I’m snowed under trying to finish off my PhD thesis…

As an alternative I’d recommend these encoders. They’re a bit expensive, and you may need to redrill the holes to get them to fit on the Dagu motors, but they work well.

Regards

Alan

How do you manage to get it to go straight? My motors just need different PWM values otherwise one is stronger. I’m trying to use redbot wheel encoders (optical encoders) to help detect each wheel speed and react accordingly, but it’s not that simple (long story).

I wonder whether I should just find some fixed values, but that would mean it would just go with same speed everytime, as it’s not possible to just find some ratio and apply it (as my experiments have shown).

What USB WiFi dongle are you using? Also, what are you using to power the robot? If you’re using non rechargeable (alkaline) batteries, could you use rechargeable (NiMh) batteries instead?

Regards

Alan

I bought my battery pack from Amazon, so had to make my own cable for the controller, but comparing to what you offer, its the same unit, so I would assume that eliminates the possibility of variations in the size of the battery pack.

I placed an order for some Dasu parts last week from a US based seller, didn’t know about this issue at the time, otherwise I could have ordered a second set of wheels to compare.

This sounds like it could be a battery problem. What type of batteries are you using to power the robot? If using 6xAA alkaline batteries then I would recommend changing to 6xAA rechargeable (NiMh) batteries.

Regards

Alan

Thanks for persevering with this. When I get back into the office on the 5th I’ll try building another robot from scratch to see if I can recreate the problem. It is possible that Dagu (the company which make the 2WD chassis) may have done something like change the wheels to use different tyres without us noticing.

I’d be interested to know if the alternative method for positioning the battery pack works for you? This seems to work well for another customer, possibly using someting like velcro to hold it in place. If it works for you then I might change the instructions to recommend it, and include some velcro with the battery packs.

Regards

Alan