different motor speeds in tanks

[betty.k]

in my recent tank experiences i ve noticed that unless you miraculously find 2 motors exactly the same, my tank will pull to one side. can i add some sort of trimpot somewhere to vary the difference in speed? will i have to add 2 trimpots, for forward and reverse? and what value (6V)?:8ball:

Edited by – betty.k on 21 November 2003 22:01:54

[betty.k]

just pushing this topic to the front!:8ball:

[Pork_Hunt]

I do the same thing with my topics.

If you were to put a variable resistor inline with the faster motor, you SHOULD be able to trim it to slow down. The only problem I can see with this, is, “what if one motor is faster forward, and the other motor is faster in reverse?”. Then you’d have to stuff around with diodes as well.
I remember a mod on tinyrc called (from memory) “infinite speed potentiometer mod”, same sort of principle.

[betty.k]

it’s only one motor that’s a little slower both forward and reverse. i thought of adding variable resistors to both wires on the faster motor, but i’m not sure what happens to the power when it goes back into the pcb after the motor, and i’ve already cooked too many pcb’s in my ‘experiments’! if this works could someone give me a ballpark estimate on value?:8ball:

[trash]

One pot should be enough, but you’d put two in, one for each motor to make life easier in the future. You’d set the pot on the slower motor to zero.
IF, you wanted to, then you could put diodes across 4 pots, two on each motor, one in each direction. The you can then adjust everything.

You’re using 6V so you have some room to waste a little bit of power. The value doesn’t matter much, because it is varible 🙂 but something about 100 ohms should be ok, trail and error.
Multiturn pots cost more, but give you more precission.

[trash]

Diodes



--+-|>|-+-|<|-+--(motor)----

|     |     |

+[/]+[/]+



Varible resistors

Edited by – trash on 22 November 2003 21:53:37

[betty.k]

ahh good, i was hoping you’d spot this post!
so does it matter which wire i attach the variable resistor to (in the case of using 1 vr per motor)?:8ball:

[trash]

no, it doesn’t matter which side of them motor you put the comonents on. You want need diodes if your only using one VR.
VR’s have 3 pins most of the time. The resistance will be the same all the time across two of them and the third is the wiper which the resistance will vary.
It doesn’t matter which way they are connected.
If you get the wrong wires on the VR, it just won’t be adjustable.

There are also two types of VR. Linear and log.
Use linear. If the control is too sensitive, try a lower value resistor. If you can’t find one, try putting another value resistor in parrallel.

[betty.k]

bewdy, thanks plenty. i’ll be using one vr per motor, i like to keep it simple:smiley2:
as always a very helpfull answer, although i didn’t quite understand the diode diagram but that’s probably because i don’t really understand curcuit diagrams full stop! thanks again:8ball:

[trash]

the cct diag is pretty simple.
Current will flow through each resistor, unless there is a short circuit across them.
Depending on which way the current is flowing, one of the diodes will be short circuit, so only one VR is in the circuit depending on if it is forward or reverse.

[betty.k]

nup. i’ve stared at that pic till it did my head in! but i understand what you’re saying, the diodes just act as one way valves and direct power to one vr or the other depending on the direction of the flow. it’s a good trick to know, but i don’t need to do it in this case. when there’s a slower motor it’s the same forward and reverse. i’ve found a couple of 100k trimpots in my junk pile and i’m about to stick ’em in. fingers crossed!:8ball:

Edited by – betty.k on 23 November 2003 21:34:47

[trash]

100K is way too big. 100 ohms is 1000 times smaller.

[betty.k]

OW!! just found out the hard way! my recent experiences have taught me to monitor the temperature of test components (with the back of my finger!).that 100k resistor sure got hot!blackeye: i’ll ge the right ones and try again:8ball:

[trash]

Ummm.. that’s the opposite of what it is supposed to be. 100K should be stone cold. BUT…
it might be a warning about what kind of 100 ohm VR you will need.

[Pork_Hunt]

I think what trash should have added is that you may need a higher wattage resistor, ie.. you may have 2watt ones and need 10watt resistors, for example. Am I right trash???

[trash]

Yes. That’s 110% correct !
I’m not sure how big they make Varible Resistors though. Even fixed resistors can get pretty big.

I get more entertainment out of hearing what betty’s doing than my own stuff.

He should still be able to use the low wattage resistors. I’ll let him have the fun of working out how to do it. 🙂

[betty.k]

sooo, i’m a source of entertainment now am i?!:clown:

i’m glad to hear that someone else is enjoying my electronical misadventures! i hope other people are learning stuff out of this too. remember, it’s good to learn from your mistakes, but it’s far better to learn from someone else’s!:p:8ball:

[trash]

Haven’t you ever owned sea monkeys ? :-0

[betty.k]

aah ha ha:D good one maaate!!
well, kind of. i lived on a dairy farm for a while and the water troughs were quite often full of mosquito larvae (wrigglers)! i trained them to fear my wrath and become my private strike force when mature! so beware, somewhere out there is a rogue kung fu ninja death squad mosquito army!

“sting ’em all, let fingernails sort ’em out”:D:8ball:

Edited by – betty.k on 24 November 2003 22:03:43

[trash]

Hahahaha…
oh yeah, that sounds like a classic.
Feed them to the tropical fish … yummy !

My cousins used to have a dairy farm too.
We used to go swimming in the the back trough.
Take our mask and snorkel and wait for the cows to come in for a drink. Cows have the lovely combination of being curious and dopey. Being petted on the nose while taking a drink, I’m supprised some of them didn’t drown.
I often wondered if some of the cows ever stopped giving milk because of crocodile impersonations.

👿

[betty.k]

yeah farms are fantastic places for curious little minds! i used to have a lot of fun playing with, ahem, flamable liquids and toys until i burnt a shed down!!blackeye:

dunno why, but farmers seem to get a bit upset about fires on their property!!:dead::8ball:

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