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Topic: logic power supplies help (Read 341 times) previous topic - next topic

Mr_Supportman

May 23, 2016, 10:51 pm Last Edit: May 23, 2016, 11:07 pm by Mr_Supportman
Hi!

Im having an issue with my project regarding power supply.

http://howtomechatronics.com/tutorials/arduino/how-to-control-stepper-motor-with-a4988-driver-and-arduino/

basicly my setup looks like that, excpet i have a Lidar Lite V2 on a spinning rig connected to the arduino driving the stepper aswell.

i power the A4988 via a 11.1v Battery and the Lidar Lite using the same battery but after a DC converter, converting it to 5V.

Everything seperate works, but toghter it dosent, so basicly my question is why?

Dose it have anything to do with the splitting of power and still sharing the same GND via the arduino?

https://developer.mbed.org/media/uploads/sventura3/pinouti2cwiring.png

my lidar wiring is like this to the 5V comming from the DC converter and the GND into the arduino.
It's all Rocket science.

DrAzzy

All grounds should be connected together.

Can you post a full wiring diagram? Hand drawn is fine, please no fritzing, we hate fritzing here.

Also, what makes you say it doesn't work? (ie, what are the symptoms?)
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Mr_Supportman

All grounds should be connected together.

Can you post a full wiring diagram? Hand drawn is fine, please no fritzing, we hate fritzing here.

Also, what makes you say it doesn't work? (ie, what are the symptoms?)
Basicly what happens is that the lidar runns fine by itself, and the stepper runns fine by itself, but when both are conected to the sme arduino, the lidar running on 5V and i2c and the stepper runing on 11.1V and a A4988 driver, the lidar gives >nack and stops after 2-5 readings. and the stepper dosent move.

i will supply a hand drawn diagram after work today, reason for the fritzing like image is Pulsedlights Lidar Lite reference image for i2c.
It's all Rocket science.

Grumpy_Mike

Sounds like a lack of decoupling on the power wiring. Alternatively it could be your power supply is not up to supplying enough current.

Mr_Supportman

Sounds like a lack of decoupling on the power wiring. Alternatively it could be your power supply is not up to supplying enough current.
Could you explain the decoupling?

I tried the same scenario using my modular power supply to recreate the situation. And gave same result.

The 11.1V battery is a 3S lipo it should be able to supply the current i need but i tested with the modular power supply just to be sure.
It's all Rocket science.

Grumpy_Mike

#5
May 24, 2016, 01:27 pm Last Edit: May 24, 2016, 01:27 pm by Grumpy_Mike
Quote
Could you explain the decoupling?
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Basically you need at least a large electrolytic across the supply for driving stepping motors. Otherwise the ripple current can be too much for the driver board's ceramic capacitor.

This is what can happen to the drivers:-

Mr_Supportman

#6
May 24, 2016, 08:35 pm Last Edit: May 24, 2016, 08:54 pm by Mr_Supportman
All grounds should be connected together.

Can you post a full wiring diagram? Hand drawn is fine, please no fritzing, we hate fritzing here.

Also, what makes you say it doesn't work? (ie, what are the symptoms?)
My hand drawing sucks but this is how it looks.
http://puu.sh/p3Jh1/afd99b4389.png
It's all Rocket science.

Mr_Supportman

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Basically you need at least a large electrolytic across the supply for driving stepping motors. Otherwise the ripple current can be too much for the driver board's ceramic capacitor.

This is what can happen to the drivers:-

Thanks for the explanation!

And thankfully the default wireing schematic for both units had capacitors included, 100uF and 1000uF

Maybe they are inadicuate?
It's all Rocket science.

Grumpy_Mike

Quote
Maybe they are inadicuate?
That should be fine. If it were me I would also include a 0.1uF ceramic capacitor across those two big ones to cope with the higher frequency.

The only thing I would change on your diagram is that you have the ground of the motor driver connected to the ground of the Arduino. There is also a common ground provided by the power supply being the same source so this wire is acting as a ground loop. I would try disconnecting this.

So the circuit looks OK maybe it is your layout giving you problems, make sure the wires for the motor are not running along side the Arduino wires.

Mr_Supportman

That should be fine. If it were me I would also include a 0.1uF ceramic capacitor across those two big ones to cope with the higher frequency.

The only thing I would change on your diagram is that you have the ground of the motor driver connected to the ground of the Arduino. There is also a common ground provided by the power supply being the same source so this wire is acting as a ground loop. I would try disconnecting this.

So the circuit looks OK maybe it is your layout giving you problems, make sure the wires for the motor are not running along side the Arduino wires.
Thanks! i will try disconnecting it!

And allso go to try everything on a breadboard ;P
It's all Rocket science.

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