Go Down

Topic: Power supply (Read 6813 times) previous topic - next topic

mpeuser

#15
Sep 02, 2010, 01:14 pm Last Edit: Sep 02, 2010, 01:23 pm by mpeuser Reason: 1
Of course you can!
You can pile up any number of any kinds of power supplies (well within some range..), and all of the will do the best to contribute a little bit of current and a little bit of voltage.

Mind that you do not connect their (secondary) grounds.
Also they might have small resistors in them that would only only allow a certain amount of current, and might also be used for current limitation.


The best rule ist to pile them from ground, starting with the highest current capabiliy... This however is somewhat logical...

Homer_Manalo

Quote
Of course you can!

Referring to my post? If you are then how is that possible since current in series is supposed to be equal?Thanks.

Grumpy_Mike

Quote
since current in series is supposed to be equal


That is only for a load, you have a generator, the current depends on the load each generator sees.

dze

hi there!

thanks for all the helpful replies.

regarding soldering, yes i think i can manage without frying myself connecting some components along with a schematic.

i feel that the way of leading a newbie along the right path, giving both pratical(buyable) solutions and a diy or hacking solutions are both good. then i can see how much i want to delve into what possibilties i have or start looking for others.

A better way is to get a ready for use powersupply which suits my needs and I hope that i can find such. Well what i have found out so far is that 'Mean Well' sell a particular powersupply for my needs; 5.5v 75 amps. that way i can connect up all six motors and run them from the same power supply.

currently i'm working with adafruit motorshield and a 12 volt motor. this is not my ideal combination, cause i would need to control 6 motors with pwm controls  and to run in sync. So after all the testing, i would be using just the arduino.

so here goes some really simple but for me mindblogging questions;

How would i connect each motor running at 5, 6 or 7.5v 12a (total 6 motors) to arduino each with it's own pwm control? say i'm using a 5.5v 46a power supply (which means i would need a 2nd one)

I'm refering to http://itp.nyu.edu/physcomp/Labs/DCMotorControl as my reference. The datasheet for L293 says it handles max 1amp, what should i use instead to handle 12amp per motor?

any advice.




UltraMagnus

Quote
And - BTW - what has this  "capacitor" to do with it??


you need to smooth the supply after rectification.

mpeuser

You will encounter a noticeable voltage drop from the H-bridge transistors at higher currents; that is why I still recommend the 7.5 volt supply....

You still have to decide for yourself, whether you want
- a simple discrete bridge
- a H-Bridge controller (+ additional transistors)
- (and that is best) a ready made board.

Here some examples of high current H-bridges
http://www.cirrus.com/en/pubs/proDatasheet/SA60U_M.pdf
http://www.pocketmagic.net/?p=508
http://www.roboticsconnection.com/p-77-10-amp-dual-h-bridge.aspx
http://www.modularcircuits.com/h-bridge.htm


BTW: I just encountered that simple explanation for H bridges:
http://www.barello.net/Papers/H-Bridge.pdf
http://www.modularcircuits.com/h-bridge_secrets1.htm

dze

deSilva@ just a short note, while reading through your links

the diy h-bridge supports up to 10A of current but the ┬ÁModule supports up to 16A. the specification is still gibberish to me. what does it mean? how do i interface with the arduino through rs-232?

are there any other boards out there, which is relatively cheap <20? that could suit my needs?

dze

also i don't need the motor to run backward or forwards, it's just one direction that i need. so maybe i do not need a h-bridge.


mpeuser

#23
Sep 03, 2010, 01:06 am Last Edit: Sep 03, 2010, 02:14 am by mpeuser Reason: 1
I think all boards for 10 to 20 amps will be > $20... They main reason is that they contain a lot of protective means, among them stall detection...

As I said many postings ago, that what you need is just a transistor; I should recommend a logic level FET type... In some posting - maybe not in this thread - I had given a small list of inexpensive ones. There must be some tutorial explaining this most simple interface..... Note that you will need a large heatsink!

Edit
----
http://www.earthshineelectronics.com/files/ASKManualRev4.pdf
Look at project 11 (and also at the other projects....)

dze

i'm currently looking at trying to diy me a motor driver for load up to 12 amp. Can someone recommend me some appropirate mosfet to suit my needs.

this link i find is pretty good but it's driving at 24 v 40 amps.
http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge

my needs are 7.5v at 12 amps. there will be six of such motors. so i think i would build single motor drivers for each motor.

there are tons of schmectics on the net about h-bridges but can someone direct me more closely (schematics and parts) to my needs?

thanks desilva, for your links and pdf. i guess i'm skipping the chapters and working towards my concept/needs.

thanks for any advice!


billhowl

If you are not control the speed of the motor, you can use relays to control the motor on/off like this
http://www.arduino.cc/playground/uploads/Main/relays.pdf
you must get relays that can switch 12A

dze

i need speed control, pwm but not direction.

Grumpy_Mike

You can use this one:-
http://uk.farnell.com/international-rectifier/irfb4228pbf/mosfet-n-ch-150v-83a-to220ab/dp/1704509

It takes at least a 10V gate signal to turn it on fully so you drive it from the arduino using a transistor with the collector resistor to 12V. It has an on resistance of 0.015R and can handle a maximum of 83A so there is plenty of margin.

mpeuser

What Mike said had been said already sometimes in this thread. Seems we are ready for another turn of the wheel..... Is this a rat race?

billhowl


This is an example of how to drive motor up to 40A using Power Mosfets Q5-Q8 by using 3 transistors Q1-Q3.
12V-24V High-Current DC Motor Speed Controller



Go Up