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1  Using Arduino / Project Guidance / Re: Arduino Control Buck Converter on: January 21, 2013, 02:13:32 pm
Well once I realized I was searching in Google for the wrong wording, I found that a LM3401 may be up my alley (or similar).  I also finally have WEBENCH working and it designed the circuit for me!  Imagine that.  All I need to do is use the Arduino to control the dimming pulse and monitor for low voltage cutoff on the LiPo.  The downside is that the circuits will not do the large selection of LiPos I wanted.  I am going to need to constrain this to the 14.8 4S 5000mAh LiPo batteries to control the 5 individual 3404, each with a Cree MK-R attached.  

Thanks,
Frank
2  Using Arduino / Project Guidance / Re: Arduino Control Buck Converter on: January 21, 2013, 01:12:13 pm
The voltage and current through the LED at any given time while energized will effectively be constant as current is forced out by the buck converter

The resaon why LED's seem dimmer is by virtue of the PWM factor and our eyes inability to discern the actual flash frequency


Correct.  However my concern is what happens to the buck converter and how do you design a buck converter to have adjustable current or as you brought up, adjustable PWM?  The Buck converter already has a switching component to control how much energy is stored in the inductor for converting a high input voltage to a low input voltage.
3  Using Arduino / Project Guidance / Arduino Control Buck Converter on: January 21, 2013, 12:48:37 pm
Morning!
I am looking to use an Arduino to control a buck converter, five independent converters to be exact, but we will just stick with one for now. I need some help with where to start, etc.

The goal is to have a controller with PWM for the new Cree MK-R so that I have extensive control over the brightness... 125mA for 20% flux to 1166mA for 150% flux. However, I can live with any current limitation beyond 700mA since I will have heat dissipation issues.

The voltage source would be LiPo 4S, 5S, and 6S hobby batteries which are 14.8v, 18.5v, and 22.2v respectively. I will have to monitor voltage since these are not protected batteries, but that is not a big deal.

Now my understanding of buck converter (my EE experience is not strong) is that I can use duty cycle to regulate the voltage on the output. So if the Arduino is programmed for the different LiPo batteries called out above, I can just use PWM to regulate the output voltage to 12v no matter the input... unless the components are not sized properly or cannot be versatile enough for this. This is where I need help in selection of of them.

Then to add on to that, how do I regulate the current or the effective on current on the LED to regulate the brightness? How does that play into the buck converter such that the circuit does not become out of balance?
4  Using Arduino / LEDs and Multiplexing / Re: where to begin? on: January 16, 2012, 04:08:38 pm
0.5A is for a voltage regulator configuration. Or so I believed.
5  Using Arduino / LEDs and Multiplexing / Re: where to begin? on: January 16, 2012, 09:47:57 am
I think I can use this thread as guidance http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1211745287 for using a DAC and OpAmp to control the LM317A's.  I just need to use a LM338 to control the power going to the LM317's.

Thanks!
Frank
6  Using Arduino / LEDs and Multiplexing / Re: where to begin? on: January 16, 2012, 08:57:01 am
LOL.  Yep!

I finally might have found something.  When I was first reading about the LM317, I missed different pieces of the documentation.

I think I will use three LM317A in an H package to drive each string from 0.5-1.8A depending on the setting.  It is likely that when all three on, I will drive them at 0.7-1A depending on what is more efficient.  When only two are on, I will run them somewhere between 1.5-1.8A depending on what is more efficient.  To get the extra current for just when a single string is on, I will switch over to the LM317A in a T package which will allow me to drive from 1.5-3.4, but I will only allow adjustment to 3.0.

Each output of the LM317 will run thru a transistor to allow me to PWM it to very the brightness.  I also have to figure out how to wire up the Arduino using a DAC to the ADJ on the LM317A for precise control.

However I now have to find regulate the overall voltage and current to each LM.

Thanks,
Frank
7  Using Arduino / LEDs and Multiplexing / Re: where to begin? on: January 15, 2012, 07:28:58 pm
Correct.  I have nothing built.  I plan on wiring it up.

My first light project was 4 Luxeon Stars in serial that I drive at 700mA using a buck driver that I have crammed into my drill battery flashlight.  I used Antec heatsink epoxy to an old Pentium heat sink.

I understand the difficulties very well, hence my struggle on where to begin.  I have been trying to find the right LMxxx regulator, but cannot find one that is adjustable within the parameters I need.  I was hoping to find one that is adjustable from 1A to 3A at 5.6-6.6VDC out.
8  Using Arduino / LEDs and Multiplexing / Re: where to begin? on: January 15, 2012, 04:34:52 pm
I guess that would help!  smiley
http://www.cree.com/products/pdf/xlampxm-l.pdf

I am basically trying to create a work lamp that I can use in the garage under the hood, camping, etc.  So I was going to put two lights every 120* around the work lamp. I can turn on just one side like a traditional drop light. Two sides for a little more flood, or all three so it is like a lantern. 

I am going to use my smaller Arduino to control the PWM for brightness, to control any current switching circuits, charging circuit for my Lithium Ion batteries, and any strobe/beacon modes.

The goal is to design and create the first open hardware and open source flashlight as a viable product to end all of these cheap lights flooding the market that are pretty much consumable.

Thanks,
Frank
9  Using Arduino / LEDs and Multiplexing / where to begin? on: January 14, 2012, 05:38:13 pm
Where do I begin with designing a circuit that will do the following?
 - Three strings of two Cree XM-L each
 - Each string is independently PWM and switched.
 - When all three strings are on, 1.0amp down each string
 - When two strings are on, 1.5-2.0amp down each string
 - When one string is on, 2.5-3.0amp down that string

The current range is flexible.

The code and most circuits are easy... this is not for me.

Thanks!
Frank
10  Using Arduino / Project Guidance / Re: New project guidance on: June 14, 2011, 06:14:27 pm
Let me see if I got it right. You are planning to charge people for a place for them to share their projects with the rest of the world, right?

Here's my thoughts...

There's no way I would join in for you to make a profit out of my work. And this comes to the other question... be careful, because sometimes, open source has the requirement that you make no money out of it, otherwise, royalties will be in order.



No.  The gadget I want to build will be open everything, however it needs to interface with a webserver to have the extra features like uploading your data, SMS messaging alarms, etc.  That webserver costs money... charging folks would only be on the order of $15/year.  The project does not require you to use the extras.  It will act as a standalone and can interface with the android app locally instead of remotely.

The open source would still stand true... we all build on each other.  The pieces I add will allow others to build and contribute back.  I will offer it as kits or fully assembled, etc.

Thanks,
Frank

11  Using Arduino / Project Guidance / Re: New project guidance on: June 14, 2011, 04:37:26 am
Quote
What about performing updates via SD memory?  Is it possible?
No, to update an arduino you need an SD card and another arduino to update the code in the first.

You have a very vague set of requirements, so much for it being open source if you won't even say what it is?

Open source doesn't mean I need to share my idea yet.  It just means I share my work for others to enjoy the DIY part of it, modify the project with additions and share with the hobbyists, etc, or even use it for similar hobbies.  I want to capitalize on the services offered and I don't want that idea out yet - not because of you all, but rather commercial folks.  I would gladly share with anyone over PM.
12  Using Arduino / Project Guidance / New project guidance on: June 13, 2011, 07:53:37 pm
Evening! (or Morning!)

I could use some guidance.  I am looking to take an idea of mine, use the arduino keeping with the open source hardware/software initiative, and market it for a specific group of people.  I do want to capitalize on the idea by the services offered on my website by allowing folks to upload, store, and share their data and experiences and even receive SMS messages or look at the data on their smartphone via an app.  The whole concept will be open source even the website half, so it can be used for other hobbyists, etc.

What kind of suggestions would you have for me on interfacing the arudino via wifi to a server and keeping it secure?  I am thinking username, password, and a pin.  Obviously the ardunio would not be able to handle a real DSA key for communications, but how secure can I get? 

What about performing updates via SD memory?  Is it possible?

Thanks,
Frank
13  Forum 2005-2010 (read only) / Troubleshooting / Re: Dynamic Pause on: January 20, 2009, 11:11:42 am
I think I need to add some more information to clarify somethings.  Plus I forgot key information.

I have the main loop that primarily grabs sensors and processes sensors.  Whenever 100ms has passed, I run a datalog routine and whenever 250ms has passed, I run a serial display routine.  

During the processing of sensors, I determine my delay which will be used when the interrupt pin is set.  Because the interrupt signal is a periodic event, it can be characterized as a duty cycle.  

While both are opposite corner case, here is something....
  • Easy case: 33.33Hz and ignore for 8%.
  • Hard case: 800.00Hz and ignore for 33%.
Obviously the hard case may not be achievable, but that doesn't matter.  

Now here is what I have to do during my interrupt in that order,
  • Begin interrupt function
  • Set pin 3 to high
  • Delay to x-seconds
  • Set pin 3 to low
  • Exit back

Now the things I have to consider is how long it takes to set pin 3 to high and then back to low before and after my delay.  Not to mention if this method of using the interrupt function is best or even going to work.  When I calculated out my max range of ignore periods, I came out to 2.5milliseconds to 0.417milliseconds of delay.

Thanks,
Frank
14  Forum 2005-2010 (read only) / Troubleshooting / Dynamic Pause on: January 19, 2009, 10:57:01 pm
Guys, I am stumped.  My code is a loop that constantly monitors and datalogs a series of sensors.  At some point, an interrupt pin will go high.  The goal is to ignore sensor inputs, and then pause for x time based on previously calculated results of the sensors, and then resume my normal loop.

I am perplexed as to how to do this because the typical time functions do not work with interrupts.

Thanks for the help.
15  Forum 2005-2010 (read only) / Troubleshooting / Re: Problems with reading A/D... on: January 19, 2009, 08:18:32 pm
Thanks folks!  That took care of it!  smiley-grin  

Lesson learned!
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