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Topic: Power LED shield (Read 10949 times) previous topic - next topic

koyaanisqatsi

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.
http://www.leddynamics.com/LuxDrive/drivers.php
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strus_fr

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

LGM-model

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  

koyaanisqatsi

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!
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LGM-model

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

LGM-model

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

koyaanisqatsi

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.  :)
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LGM-model

>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.

koyaanisqatsi

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.
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strus_fr

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 ...

koyaanisqatsi

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.
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koyaanisqatsi

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.
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strus_fr

Hi,

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

Thanks !

koyaanisqatsi

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.
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koyaanisqatsi

I've placed my orders for the PCBs and parts!    :D  ;D  8-)

Lead time is about two weeks, during which I will get my store up and running and try to produce some documentation.
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