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496  Using Arduino / Motors, Mechanics, and Power / Re: Driving a solenoid on: March 29, 2011, 10:45:06 am
Thanks for explaining that for me.
497  Using Arduino / Motors, Mechanics, and Power / Re: Driving a solenoid on: March 29, 2011, 09:57:58 am
Here is a very nice logic level mosfet available in the US.

http://www.sparkfun.com/products/10213
I am using this as in the drawing in post #6 (with the source and drain corrected).  But Sparkfun's example has R1 setup up different, in this example:
http://www.sparkfun.com/datasheets/Components/General/MOSFET-Power-Control-v10.pdf

Is one better than the other, or will they both work the same?
498  Using Arduino / Displays / Re: Power source on: March 28, 2011, 01:16:12 pm
Thanks, I thought so, but wanted to be sure.
499  Using Arduino / Motors, Mechanics, and Power / Re: Using the SN754410 on the adafruit motor sheild on: March 28, 2011, 12:39:20 pm
Quote
On using the SN754410: Some people use the SN754410 motor driver chip because it is pin-compatible, has output diodes and can provide 1A per motor, 2A peak. After careful reading of the datasheet and discussion with TI tech support and power engineers it appears that the output diodes were designed for ESD protection only and that using them as kickback-protection is a hack and not guaranteed for performance. For that reason the kit does not come with the SN754410 and instead uses the L293D with integrated kickback-protection diodes. If you're willing to risk it, and need the extra currrent, feel free to buy SN754410's and replace the provided chips

What if I add my own flyback diodes (1N4007), would it then be perfectly safe to use the SN754410?
But is it possible to add these diodes to the circuit and still maintain a reversible motor?

Look at the datasheet:

http://www.datasheetcatalog.org/datasheet/texasinstruments/sn754410.pdf

Also look at the datasheet for the L298N for how to hook up the diodes (it has a clearer diagram for DC motor h-bridge control).

Basically, the connection for a DC motor is (bad ascii art ahead!):

O1 ---------------+
             D1   |    D2
    GND ----->|---+---->|---- +VS
                  |
                Motor                 
             D3   |    D4
    GND ----->|---+---->|---- +VS
                  |
O2 ---------------+


Where O1 and O2 are the outputs from the h-bridge, D1-D4 are the diodes, GND is ground, and +VS is the DC supply for the motor.

The only thing about the datasheet for the SN754410 is that it doesn't say whether to use high-speed Shottky diodes or not; the 1N4007 is not such a diode. It might work OK - I'm not sure (go for Shottkys if you can for this app - they don't really cost all that much more).


Thanks for this info.  I'm adding it in now, can you take a look at this drawing and make sure I've got the diodes oriented right, going to ground or voltage at the right places...
500  Using Arduino / Displays / Power source on: March 28, 2011, 11:02:25 am
I'm powering my SparkFun 1602 LCD from a 7805, powered by a +12v adapter.  I'm also powering my Uno from the +12v adapter.  So the ground is common to the Uno and the LCD. 
My question, if my voltage into the Uno goes to the Vin and Gnd pin right next to it, can I safely use the ground pin next to D13 to ground my LCD, and LCD backlight?

In simpler terms, the voltage my LCD uses has to get it's ground by going back to and through the 2 ground pins on each side of the Uno board.  This should not be a problem for the amount of current an LCD uses should it, nor will it cause any type of inductance or something that I don't know about?
501  Using Arduino / Displays / Re: Quick urgent PWM question on: March 26, 2011, 11:34:40 pm
Thanks for the good schema, rugged!
502  Using Arduino / Displays / Re: Using Pin 13 for LCD on: March 26, 2011, 11:32:30 pm
With a very tight home pcb in the making, it's quite beneficial to use pin as the enable instead of an other.  If you haven't had any problem with DAC, I doubt I ever will with the LCD...
503  Using Arduino / LEDs and Multiplexing / Re: fading a light on: March 26, 2011, 01:05:58 pm
THANKS!
I was on pin 12
Too bad all problems aren't that simple!
504  Using Arduino / LEDs and Multiplexing / fading a light on: March 26, 2011, 11:37:56 am
Can someone please tell me what IC to use to fade this:
http://cgi.ebay.com/ebaymotors/LED-STRIP-30CM-BRIGHT-EFFICIENCY-REPTILE-LIGHT-12V-RED-/140399018407?pt=Motors_Car_Truck_Parts_Accessories&hash=item20b06f01a7#ht_5317wt_939

...I've tried using the mosfet:
http://www.sparkfun.com/products/10213
...but it doesn't fade, it just is either ON or OFF

I've searched for fading, but find thousands of topics.  If someone could just tell me what chip I need, I can search it out.
thanks,
505  Using Arduino / Displays / Using Pin 13 for LCD on: March 26, 2011, 01:51:17 am
Will there be any unforeseen problems using pin 13 (that has the built in LED) to operate my 2x16 LCD display's pin 6 (H/L Enable signal)?
506  Using Arduino / Displays / Quick urgent PWM question on: March 25, 2011, 10:59:15 am
HOPING TO ETCH MY BOARD TODAY, AND NEED ONE THING VERIFIED:
I'm wanting to fade Spakfun's 16x2 LCD display.  the specs are:
LED forward voltage  4.2   (4.6 V max)
forward current 120    (160 mA  max)

I had it prototyped on my board through a 100 ohm resistor off a PWM pin from the Uno and it seemed to fade in and out okay, but for 120 mA, shouldn't I have a transistor drive it or something, since the I/O pins are limited at 40ma?
I have the backlight negative connected to ground, the positive goes through the 100 ohm resisitor to a jumper that I can switch from either 5+, or to the D0 pin. With this config. what transisitor & bais resistor would I need coming off the D0 pin?
If someone could recommend what transistor to use, I don't understand them all together yet.  Not sure if I need a PNP or a NPN for this type of config.  I have a lot of common transistors, just don't know which one I need to use here.
Thanks
507  Using Arduino / Motors, Mechanics, and Power / Re: Using the SN754410 on the adafruit motor sheild on: March 24, 2011, 09:05:09 pm
OH!
Okay, I will incorporate them in then.  Some 1N4005's are laying around here.
508  Using Arduino / Motors, Mechanics, and Power / Re: Using the SN754410 on the adafruit motor sheild on: March 24, 2011, 09:00:48 pm
Thanks.  I think I'll 'risk' it then without them.
509  Using Arduino / Motors, Mechanics, and Power / Using the SN754410 on the adafruit motor sheild on: March 22, 2011, 10:40:40 pm
Quote
On using the SN754410: Some people use the SN754410 motor driver chip because it is pin-compatible, has output diodes and can provide 1A per motor, 2A peak. After careful reading of the datasheet and discussion with TI tech support and power engineers it appears that the output diodes were designed for ESD protection only and that using them as kickback-protection is a hack and not guaranteed for performance. For that reason the kit does not come with the SN754410 and instead uses the L293D with integrated kickback-protection diodes. If you're willing to risk it, and need the extra currrent, feel free to buy SN754410's and replace the provided chips

What if I add my own flyback diodes (1N4007), would it then be perfectly safe to use the SN754410?
But is it possible to add these diodes to the circuit and still maintain a reversible motor?
510  Using Arduino / LEDs and Multiplexing / Re: Controlling 2-4 LED's on: March 16, 2011, 05:05:05 pm
I guess I won't really need the high power LEDs.  Here's what I plan to use:
http://cgi.ebay.com/ebaymotors/LED-STRIP-30CM-DRL-DAYTIME-RUNNING-LIGHT-AUDI-BLUE-12V-/130394189542?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e5c196ee6#ht_5317wt_939

...I shouldn't need anything but the RFP30N06LE MOSFET to use this since my power supply is 12 volt and it is made to connect to automotive 12 V.
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