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15106  Forum 2005-2010 (read only) / Interfacing / Re: analog out 0-10V With Arduino for lighting control on: March 05, 2009, 09:49:23 pm
is there another issue i am missing?

No, that should work. However as already posted, using a single common emitter transistor will result in a reversal of control action. That is at 0% duty cycle in software the control voltage will be full Vin voltage output and 100% duty cycle will result in near zero voltage output. Just makes the software a little more tricky, but not that big a deal. Biggest concern is if Vin is over 10vdc then the control voltage to the ballast will also be over 10vdc, does this cause any harm to the ballast controller?

15107  Forum 2005-2010 (read only) / Interfacing / Re: Powering from external source? on: March 03, 2009, 12:40:33 am
You don't want to wire to the Vin pin on the Arduion as it must be at least around 8.5 volts to power the Arduino on board voltage regulator correctly. USB is 5vdc only so you would wire the +5vdc from somewhere inside your external USB thingy to the Arduino 5V pin. Also wire from an Arduino gnd pin to the USB thingy's inside ground.


15108  Forum 2005-2010 (read only) / Interfacing / Re: controlling multiple relays on: March 03, 2009, 10:11:04 pm
Good. I did a little research on the FT232R USB convertor chip's web site and it appears that while the chip has 'hooks' to make additional USB current avalible, however the Arduino's simple design does not utilize this feature so the on board 5vdc current limit is 100ma total, so an external power source is required for anything requiring over that amount, minus what the Arduino board itself requires.

Good luck

15109  Forum 2005-2010 (read only) / Interfacing / Re: controlling multiple relays on: March 03, 2009, 09:16:02 pm
It appears that the current requirement for your relays is 91 ma each, or just over 1/2 amp total for all six. So a 1 amp 5vdc external power supply should work well. Also be aware that you will need some kind of switching transistor between the Arduino output pins driving these relays as the current limit for a output pin is 40ma or less.


15110  Forum 2005-2010 (read only) / Interfacing / Re: controlling multiple relays on: March 03, 2009, 08:54:21 pm
First we would have to know the current demands of each of the 5vdc relays, do you have a spec sheet for the relays? If not too high then it is possible that the Arduino's 5vdc power could be used. If the total current requirements for all 6 relays (assuming that there is situations where all five must be activated) is too much for the Arduino's internal power limits then ONE external 5vdc supply would work fine assuming it's maximum current capacity is equal or greater then the demand for the 6 relays, there is no need for 6 separate 5vdc supplies.

The biggest problem is the Arduino's 5vdc current capacity is different and much less when being powered from the USB cable Vs using an external power pack plugged into the Arduino.

Anyway see what you can find out about the relay's coil resistance or current requirements, the best solution will follow having that information.


PS: I've asked this question before but not received an answer yet. What is the 5vdc current limit of the standard Arduino board when using just the USB cable? 100MA?, 500MA? I assume the answer lies with the FT232R USB controller chip and what it asks for in additional 5 volt current if any from the PC's USB controller?
15111  Forum 2005-2010 (read only) / Interfacing / Re: Linear motion sensing/controlling on: March 02, 2009, 05:34:29 pm
Hi T_Hum, welcome to the forum.

One final question with regard to SSRs.  I know that there are plenty of ssrs that can be controlled with 5VDC.  That is simply to drive the relay correct?  I can switch any load I want as long as its within the load rating of the SSR?  Also, what is needed(if anything at all) to isolate the arduino from the SSR to avoid any sort of damage to the board?  For the record I need to switch 12VDC @ approximately 10 amps.

Those commercial SSR use an internal optical isolator so you need no further protection for you Arduino. One thing to consider is that to use those SSRs at their maximum rated current requires that you mount them to a heat sink. The back side of the SSR cube has a metal conduction plate that needs to be in good mechanical contact with the heat sink an a application of heat sink paste is called for. If you need a max of 10amps for your AC powered device use a SSR rated for higher then that, say 20 or 30 amps. It's not good to use components at their 100% rated value and normal engineering practice is to not utilize maximum values but rather to use a larger value component.

EDIT: PS I just reread your post and want to make sure you understand that most of those SSR are for switching AC voltage only, not DC. To switch high current DC devices a logic level MOSFET is a better choice.
Make sense?

15112  Forum 2005-2010 (read only) / Interfacing / Re: Transistor Help on: February 27, 2009, 06:01:28 pm
Both the IRF530 & IRF510 are not logic level MOSFETS and require a full 10vdc gate to source voltage to fully reach their rated maximum current.

A logic level MOSFET will have a lower gate/source turn on threshold such that the Arduino's logic high voltage will fully turn the device on and lower the heat disspation of the MOSFET. A BUK-555 is a nice choice:

15113  Forum 2005-2010 (read only) / Interfacing / Re: Transistor Help on: February 27, 2009, 04:01:38 pm
I think that you might be pushing the max current rating of that transistor too close. Heat sinking would most likely be required depending of the duty cycle you run the motor at.

 I would recommend you search around for logic level N- channel MOSFET switching transistors. They are much easier for the Arduino to drive and have less voltage drop when switched fully on.

15114  Forum 2005-2010 (read only) / Interfacing / Re: Cool LCD controller found on E-bay on: February 27, 2009, 03:54:36 am
Hi Lefty, that link doesn't work for me.

Fixed the link I hope. Your links are OK but there priced somewhat higher and the I2C controller doesn't have a TTL serial mode and only handles a 4X3 matrix keypad.

 The keypad I show is real thin, .040 inches thick, 3" tall X 2.7" wide. It's designed to be glued or double tapped to a flat surface and only requires a .012" X 1" slit to pass the flat flex cable trough. No sign of contact bouncing so the controller is handling that well. Good cheap keypad, decent quality for the few bucks.

15115  Forum 2005-2010 (read only) / Interfacing / Re: Cool LCD controller found on E-bay on: February 26, 2009, 06:20:49 pm
Well the serial LCD controller arrived today and I quickly wired it up to my breadboard to a USB serial converter module and tested it out with my windows terminal program. Everything worked out of the box.

 Only initial problem I came across is that the serial controller has male pins for the 18 pin connection to the LCD and my LCD has male pins also, so that was a no go. So I chopped up a 40pin IC socket and solder it back to back as a female to female connector so everyone could play nicely together.  smiley-wink

As a coincidence I had ordered a 4X4 keyboard matrix the same day I order the LCD serial controller and it to arrived the same day, it coming from Hong Kong. It has a connector that hooks right up to the serial control, no wiring changes needed. The controller has an interrupt pin that your micro can scan or interrupt with when there has been a key button pushed and then there is a serial command you send to the controller that then sends back the value of the button (0x01-0x10) via the serial interface. Very cool. This whole setup is a real pin saver for the Arduion for all the functions it can do. The serial controller has quite a few graphic commands that can allow one to do quite a few things with.

 Anyway highly recommended, it's a good price, does what it says, can work as serial or I2C and the built in matrix keypad scanner makes for a super low cost terminal interface for your Arduion applications.

Here is the matrix keypad I bought:

15116  Forum 2005-2010 (read only) / Interfacing / Re: Cool LCD controller found on E-bay on: February 21, 2009, 05:07:41 am
Do you know if it is made so that you can have more than one of them on the same I2C bus ?

Yes you can reassign it's I2C address: From data sheet

"Each device must have its own unique address (ID). The address range is from 'A' to 'Z' (HEX
from 0x41 to 0x5A). Default address shipped from the manufacture is 'L' (0x4C).
The address can be easily changed by send the command “Set the new device address”.

15117  Forum 2005-2010 (read only) / Interfacing / Cool LCD controller found on E-bay on: February 21, 2009, 03:19:40 am
I just ordered one of these last night. It will mount onto the back of most common LCD modules. You can select either I2C or serial communications mode and it has built in keypad scanning interface for a 4X4 keypad. Lots of features your just a few bucks.

15118  Forum 2005-2010 (read only) / Interfacing / Re: Uploading with the RS232 Serial port on: February 26, 2009, 06:02:13 pm
It won't work directly, there has to be some form of level switching such that the Arduino doesn't see the negitive and too high voltages that the RS-232 uses.

 My suggestions is to just get this RS-232 Arduino clone kit, it's cheap and you never can have too much Arduino around. I've been using this board for some months now and it works great, I even upgraded it to a 328 chip.

15119  Forum 2005-2010 (read only) / Interfacing / Re: Creating a case/housing for my project? on: February 25, 2009, 02:18:03 pm
Some have, most don't I think. Hobby stores sell small quarter round and half round wood trim material in balsa and sometimes spruce. This can be cut at angles like a picture frame and painted or stained to make a decent looking bezel.

15120  Forum 2005-2010 (read only) / Interfacing / Re: Creating a case/housing for my project? on: February 25, 2009, 01:54:55 pm
A trim bezel on the outside can hide a rough cut rectangle for the display.

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