"Proper" mixing is open to debate :-).
An issue is that you have to make decisions about how fast a track is moving under pure signals from a single pot and what to do when signals from the other pot are included. For example, if you push the FB (Forward-Backward pot fully forwards, and if both motors then run at full speed ahead, how do you deal with the addition of a small amount of LR (Left-Right) pot being added. To get rotation you have to have one track going faster that the other. So, if you are already running at maximum forwards speed on both motors you must decrease one or other track speed in order to turn. But, if you had been standing still you would have accelerated one or other track to achieve the same result.
So, all that said, here is a simple off-the-cuff starting solution out of my head which seems like good start.
If pots are mechanically independant then both can be at 100% simultaneously.
If both are on a joystick type arrangement, if Yaxis = 100% and Xaxis = 0%, then adding some B will usually reduce A. A joystick could be constructed where the above is not true, but these are unusual.
Assume that the joystick is of the type that increasing Y% when X = 100% will reduce X. Other assumptions can be made.
FB = front-back pot. Centre zero, +Ve for forward motion of pot
LR = Left right pot. Centre zero. +Ve for pot at right.
K is a scale factor initially 1.
If any result exceeds 100% then adjust K so result = 100% and use same K value for other motor also.
- eg if Left motor result = 125 and Right motor result = 80 then.
As 125 x 0.8 = 100, set K = 0.8. Then.
Left = 125 x 0.8 = 100%. Right = 80 x 0.8 = 64%.
Then:
Sanity checks:
LR = 0 (centered), FB = full fwd -> Both motors run full forwards.
LR = full left, FB = 0 ->
Left motor runs full backwards,
Right motor runs full forwards.
Vehicle rotates anti clockwise.
FB was 100%, Lr = 0%. Add 10% of LR to right.
L = FB+LR = 100%- + 10%
R = FB-LR = 100%- - 10%
If largest axis < 100%, scale until = 100%.
Then scale other axis by same amount.
Best Answer
From the documentation, it looks like there is a buffer on the relay board.
From some googling around - On the phidgets forum:
Also:
It's worth noting that the documentation for that board is terrible. I can't find the schematic anywhere. I'm guessing as to how the board works, based on the fact that it seems to have two ICs on it, and the controller it's connected to doesn't seem to have the facilities to drive the relay coil.
Really, I would strongly suggest you e-mail the manufacturer, and ask for the schematic. If they refuse, return the board, and don't purchase from them again.
Re: "Load Noise"
This is incorrectly titled. What they are really talking about are inductive loads.
If your fish-tank lights use electronic ballasts, you're fine. Also, your bulbs are small enough that even with magnetic ballasts, I think you can probably get away without any sort of inductive kickback suppression.
You can tell if you have an inductive or electronic ballast simply by weight. If the ballast feels like it's got a bunch of steel in it (the ballast inductor), it's magnetic. If not, it's electronic.