help with motor driver l293d power

J

James Venning

New Member
hi all,

I have recently purchased an 18 pin picaxe, l293d motor driver, and the board (i think it's chi035) to go with them. I've had no trouble mucking around with LEDs and so forth, but now I want to use a motor.

in the manual, it says I can connect another 6v to the board to add to the output voltage. but in another manual it says "Only a single 4.5-6V supply should be used with motor outputs." so this is the normal 3 x AA battery supply?

how can I get more voltage output to my motors?

Thanks in advance,
James
 
J

James Venning

New Member
thanks for your help. I cut the resistor as the diagram showed, and moved my 3 AA power supply to the left hand side of the board, replacing it with the 2 cables from my power supply. now i can't get it to work. it will still download from my computer, but when i try to run it it doesn't work. I have the 2 motors i'm simply trying to make go forward in pins 4,5,6 and 7 on the right hand side of the board, and they worked there before. my code is just high 4
high 6

any suggestions?
 
J

James Venning

New Member
and another thing, what are the 'darlington outputs'? the manual says "If a higher voltage (e.g. 12V) is required to drive the FET or darlington outputs,
two separate power supplies may be used." I'm not using the FETs (should I be), but i'm not sure what the darlingtons are...
 
R

Rickharris

Senior Member
James Venning said:
and another thing, what are the 'darlington outputs'? the manual says "If a higher voltage (e.g. 12V) is required to drive the FET or darlington outputs,
two separate power supplies may be used." I'm not using the FETs (should I be), but i'm not sure what the darlingtons are...
Click to expand...

Check the interface PDF file for Darlington Manual 3 page 15
 
H

hamchapman

New Member
I'm not really sure why you're using darlingtons.

Is your problem that you don't know how to wire the PICAXE Chip to the L293D?

Or is it just that you want more voltage to go to the motor, through the L293D?

If it's the first then I can help you. If it's the second, then I assume you just need to wire up the L293D to a higher voltage supply. In the project I'm doing at the moment I have a 4.5V supply for the PICAXE Chip and then another 4.5V supply for the L293D, although I would prefer to be using 6V. 4.5V for both seems to work fine.
 
J

James Venning

New Member
i don't know if i'm using darlingtons or not...

at the moment i have 2 power supplies connected to the CHI035, 3 x AA batteries to the 'PIC', and a 6/7.5/9/12 V transformer connected to the 'PWR'.

i have no inputs

my outputs are the 2 motors in 'A' (4 and 5) and 'B' (6 and 7). I cannot get the outputs to work now though...
 
H

hamchapman

New Member
I think all you need to do to test it is put in this code:

Code: 
start
let pins = 80
wait 5
let pins = 0
wait 5
goto start
That should just turn both motors on in the same direction and then turn then off, then repeat.
 
H

hamchapman

New Member
Do the motors work independently when you just touch a positive and negative to them?

They should I think.

I assume you can still download to the PICAXE Chip? If all of that works then it sounds like you might have wired up your L293D Chip incorrectly. Or it isn't getting power altogether.
 
J

James Venning

New Member
okay tried something as simple as i could think of.

i plugged a small torch globe into output 3, and ran this program:
high 3
pause 1000
low 3

now i ran a similar program before i changed to two power inputs, and it worked fine. I checked the transformer by plugging it straight into the globe, which worked fine. now i downloaded that program and ran it with the transformer at 6v, and it didn't work...
 
J

James Venning

New Member
"If all of that works then it sounds like you might have wired up your L293D Chip incorrectly. Or it isn't getting power altogether." I don't think it's wired up wrong, I have the started board so I just put the chip in the socket. Plus it was working before I changed to 2 power supplies, so I don't think it's wired wrong.
 
H

hamchapman

New Member
There should be a common ground between the L293D and the PICAXE chip. Also there should be a shared positive between the two chips as well. But the L293D should also have an independent positive supply.

If you just plugged the stuff into the board but then changed the power supplies, I'd guess it's just a power supply problem.
 
J

James Venning

New Member
hamchapman said:
If you just plugged the stuff into the board but then changed the power supplies, I'd guess it's just a power supply problem.
Click to expand...
I did just plug it in, and then later changed the power supply. both power supplies work independently though...

I'm a bit worried by the phrase in the manual "Only a single 4.5-6V supply should be used with motor outputs." This was my original question, but eclectic said to just do what a diagram earlier in the manual said, which I did, now it doesn't work...
 
E

eclectic

Moderator
James.
Can you please check WHICH board you have?

The CHI035 has a L293D chip and four large flat transistors (with holes).

The CHI030 has a ULN2803 chip and NO transistors.

Could you confirm please?

I've got a CHI035 working here now, using two separate power supplies.

e.
 
H

hamchapman

New Member
From what you said earlier, it sounds like all of the indivdual components still work. But they don't work together.

*Hopefully* I have attached an image of a circuit I changed a bit. This is (sort of - at least power supply wise) how you should be set up.

 
E

eclectic

Moderator
James. Thanks for the clear photo.
My setup is similar.

Look at the CHI035 Datasheet drawings for further reference.

One CHI035 board. Resistor R9 cut out.
I'm using the screw terminal blocks as shown on page 5.

V1 Left hand supply = 2 x AA NiMh (c. 2.5v)

A small 6v Solar-type motor. Leads connected to outputs 4 and 5.

The program below downloads, but will not turn the motor.

Code: 
main:
pins = 0
pause 2000

pins = %00100000
pause 2000

pins = 0
pause 2000

pins = %00010000
pause 2000
goto main
I then connected 4 x AA NiMh to the right-hand V2 terminals.
Then the motor worked.
e.
 
L

Logic Rules

New Member
James,
I don't mean to sound ill mannered but one must read the documentation for the devices they are trying to use. it does provide some help.
you are coming out of left field with a question that is coverered in the mauals.
Check manual #2 for commands, and manual#3 for intefacing.
I do hope this providws you with some help.
Regards, logicrules
 
J

James Venning

New Member
Logic Rules said:
James,
I don't mean to sound ill mannered but one must read the documentation for the devices they are trying to use. it does provide some help.
you are coming out of left field with a question that is coverered in the mauals.
Click to expand...

I've read and re-read the manuals. When they say "you can add another power supply" and then 2 pages later say: "only use a single power supply" that's what I don't get...

why the contradiction?
 
premelec

premelec

Senior Member
There is no particular contradiction - just various circumstances; it boils down to understanding the circuit functions you are trying to make work. Sometimes a motor will have different voltages and currents [usually higher!] than the controlling PICAXE and good practice will isolate the PICAXE power supply and motor power supply so that the PICAXE is not controlled inadvertently by the transients generated in the power bus by the motor instead of the desired effect of the PICAXE controlling the motor! For low voltage and current motors only one supply often works fine. Pay attention to the circuit rather than the text and make sense out of that... persist!good luck!
 
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