Power LED shield

Progress report:

Shopping cart installed. Needs to be configured. Will post the link when it's usable.

Found pin headers that solve the clearance problem, but they are EXPENSIVE and don't have sockets on the top, so I'm not happy with them. Board design may have to change depending on what I find for solutions to this problem. Posted about it here: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267383978

Got some prices for the bill of materials. LGM-model has been a great help with that, thanks! Still getting all my ducks in a row for a kit.

The PCB is close to ready for fabrication. As soon as I solve the clearance problem, I'll send it out and it should be ready for sale within a few days of receiving them.

Stay tuned!

Finally what are the pins used?
I have to know If I am buying an arduino mega .. or not. :slight_smile:
Thanks

It's designed for the Duemilanove on pins 3, 9, 10 and 11. See my first post for all the basic specs.

Hello,

Are you sure your digital logic is correct as show in the schematic?
I used the signal from Arduino to make the Gate go high/low and the input +5 with the result that the output is inverted...
No?

The pucks have an inverted input requirement on the CTRL pin: +5v to the CTRL pin will shut off the LED and an 'open circuit' or GND on the CTRL pin will drive the LED at maximum current.

When the PWM signal is HIGH, the opto-isolator clamps the REF (+5v) pin to the CTRL pin, shutting off the LED. When it is low, the opto-isolator goes open and the potentiometer provides a small voltage from the REF to the CTRL pin to control the current to the LED - and thus the maximum LED brightness.

The easiest way to handle this in your code is to work with it as if there was not an inverted input and then use map() to invert your value right before you analogWrite() it like this:

ledPWM = map(ledPWM,0,255,255,0);

Hi,

I have a question about the power source needed.
In the first post, you are saying:

  • Input voltage range 5-32 VDC
    To drive 2 buckpuck with 6 leds on each (1000mA), can you confirm that my current power source: 24V (2.5A) will match?
    Thank you!

I can help you with that, but I'll need some more information:

o A schematic on how you intend to connect the LEDs to the BuckPucks. I specifically need to know whether they are being connected in series, parallel or a combination. (or let me know if you need me to tell you how to connect them)
o The voltage drop and current rating of each LED. Better yet, post a link to the data sheet for your LEDs

Also, have you studied the data sheet on the BuckPucks? They have a few good examples on how to hook up some common LEDs.

Hi,
ok I will try to do the math myself. Thanks

koyaanisqatsi

Re the digital signal, your post #43. Yes I agree with your description of the how the power puck works. And I agree, your solution within the code is the most elegant.

However, I was referring actually to the schematic use of the M74HC125 Quad Bus Buffer. The way I read the schematic, it does not invert the input. I built this up with the digital signal on pin 1 (1G) , +5 v on pin 2 (1A) and the on to the optoisolator on pin 3 (1y).

Charles

Ah! I see what you're doing - drive the !OutputEnable pin and hold the Input pin high in order to invert the PWM signal going to the puck. I never realized it could be done like that.

I like that! I was also recently thinking of changing out the 74-125 for an inverting buffer. Your solution does it without changing the part, but if there exists an inverting buffer with the same pin-out, I'll just change it out for that. Otherwise I'll update the schematic as above.

Having to keep track of the inverted PWM value in code can be a pain, especially when you're not using the entire range of PWM or having to map it against some other range of values. For a while I didn't really care. But as I ran into more problems with it, it started to really annoy me.

Thanks again for your help!

Here are some pictures of my prototype board made from your schematic and the fiber optic Illuminator.


I think you saved me from blowing up my first Arduino! Great to collaborate via the forum. For others, the design works and it is a PITA to make your own board! I look forward to seeing the kit or PCB soon. Thanks to all. Charles - lgm3d.com

RE inverting the Arduino signal you might be able to use this chip - DM74ALS1005N I think. It is simply a Hex Inverting Driver, not a tri-state.
http://www.fairchildsemi.com/ds/DM/DM74ALS1005.pdf
The pin out is not identical but it might simplify things a bit as it only needs Vcc on 14 and Gnd on 7. No gnd or + per logic circuit

Charles

Very cool! I'm stoked you were able to get my schematic working for you.

I took a look at your site. I might now have an idea what you are building - red, yellow, green and white make for the typical colors of a city lighting plan. White for street lights and windows, and r/y/g for traffic signals. No?

I'm looking at the DM74ALS1005N and a couple other hex buffer/inverters. With an open collector output, the output logic state can be inverted or not by me, depending on how I connect it to the opto-isolator. If I invert it, the circuit gains some efficiency. I'm also looking at the SN74LS07 (http://focus.ti.com/lit/ds/symlink/sn74ls07.pdf), which is the cleanest option because it's non-inverted and I would invert it in the schematic, but it costs 90 cents a pop. Then there's the MC74AC05 (http://www.onsemi.com/pub_link/Collateral/MC74AC05-D.PDF), which is 1/3 the cost, but I can't invert it and will have to eat the efficiency loss. Decisions, decisions. :slight_smile:

White for street lights and windows, and r/y/g for traffic signals. No?

Something close to that. You saw I had to scrub the customers logo off the control panel. This one is a trade show and sales display for a new product.

My only thoughts on the IC is to get something that is readily available and in stock most of the time at several places. It stinks when you design something and have 5-10 kits sitting around with one part that you can no longer get. Been there.

OK, I found what I'm going to use in place of the 74-125: Good ol' Quad NAND gates.
MC74AC132 (http://www.onsemi.com/pub_link/Collateral/MC74AC132-D.PDF)

It solves the inversion annoyance, is cheaper, looks like it will be around a long time and can drive up to 24mA.

hi,
Do you have an idea when we will be able to get some shields?
I am looking at this date to roder my LEDs ...

I'm finishing off the last couple bugs and trying to finalize the board this weekend. If I can send it out to fabrication this week, I should be able to ship the boards by the end of the month.

The problem with clearance over the Arduino USB port has been the worst to overcome. Today I rearranged the layout so that there are no pins around the USB connector. It forced me to make the PCB a little bigger though, which will increase the cost. I'm trying to squeeze everything in as close as I can for the smallest board possible.

Power LED Shield v1.6:

http://www.chesterfamily.org/pictures?g2_itemId=10108

It not only solves the clearance problem over the USB port, but actually turned out smaller than any of my previous designs. It also has holes in the right places to match the Arduino and the connections for the LEDs are properly ordered + and -. So I'm really happy with this layout.

I'm going to proof/QA it and will send it out as soon as possible.

Hi,

Perfect timing, I am ready for it!
Could you put on your web site when ready a movie of it working?

Thanks !

Certainly! I'm ordering a batch of PCBs and some sets of parts too so I can offer a PCB only, a kit and maybe a fully completed board. I will have at least one board completely built so I can demo it and take pictures and videos.