I am in need to a shield that can drive 2 RGB LED strips. 12V, typical draw 2.5A, the ones from Amazon!
I know its a simple circuit with a FET and PWM output (Yes, I need dimming), but I am surprised that there is no shield for it.
Do my google skills really suck or there is actually no ready made solution for this?
-AM
I suspect the problem is that the total current draw would need to be 7.5A. That's quite a lot. Any shield would need its own power socket, as it would not be practical for the Arduino to provide any shield with that much current, regulated or otherwise, at any voltage. But it would not be too difficult to make your own shield from stripboard. Your shield would have its own power socket and it would in turn provide power to the Arduino's own regulator.
Also I see you have posted the same question twice. That's not really considered good manners here, but newbies are treated with forgiveness (the first time ;)).
Paul
Sorry for the duplicate thread! Dont know what happened there!
Can someone please merge them in one or guide me how to do that!
Yes, I would need a separate power input on the shield because the LEDs are 12V. ignoring the total current draw.
I am thinking of splitting this into 6 separate channels which would achieve 2 things:
The issue I am struggling with a do I use up all the 6 PWMs on Arduino ?
Or maybe I can do that for the first rev and then enhance it to be stack able and free up Arduino PWM pins!
I am still surprised that no one has already done a shield like this ? It would be a pretty general purpose high current PWM shield.
Can use PWM pins, can do software PWM.
Once you get past 35-40 Hz, the LEDs just look on, so not much point going to high speed PWM for that.
More than the speed I am concerned about Arduino getting too busy doing just the LED stuff.
I plan to use this Arduino for a couple of other things too in the kitchen!
Gas sensor, under sink water detector, temp detector to control the chimney exhaust.
So if I can offload the Arduino from PWM, I would prefer that.
But all of this is rev 2 of the design, for rev 1 I am just going to plop 6 such circuits and make the shield non-stackable!
Do you see any issues?
What you want sounds as if it may be available already in a motor control shield.
So why 6 channels? Your explanation earlier about higher voltages and currents did not sound relevant to me. The only reason for needing 6 channels would be to mix 2 colours at once (3 channels for each RGB combination). Any Arduino can do this with almost zero load on its computing power. Switching higher voltages or currents is just a matter of choosing the right components, as you said.
Paul
Paul__B:
What you want sounds as if it may be available already in a motor control shield.
PLEASE point me to it if you see something similar. I have looked and looked and looked again.
I even found a 16 channel PWM version but the max current is 1A per channel (16A) total. Thats no good to me because my LED strips are 5m in length and the current draw is ~2.5A for the non-RGB ones.
PaulRB:
So why 6 channels? Your explanation earlier about higher voltages and currents did not sound relevant to me. The only reason for needing 6 channels would be to mix 2 colours at once (3 channels for each RGB combination). Any Arduino can do this with almost zero load on its computing power. Switching higher voltages or currents is just a matter of choosing the right components, as you said.Paul
I was thinking 6 channels because if I am going to go through the trouble of making a shield, I want to make sure that I can drive at least 2 RGB LED strips in every possible way.
I found something VERY close to what I am trying to do but it peaks out at 1A per channel, I need more than that!
Here is what I am trying to do http://www.ledsee.com/index.php/new-products/16-channel-i2c-fet-arduino-schield-pca9685-detail?showall=1
Just higher current per channel. This might be good for LEDs but I want to drive LED strips.
Here are the strips I am talking about http://www.amazon.com/Flexible-Changing-Ribbon-Ledwholesalers-2034rgb/dp/B00476B908/ref=pd_sim_hi_1
Ok, so you are prototyping on breadboard first?
Sugguested parts list (enyone feel free to chip in if I miss anything or suggest anything unsuitable):
6 irl520 (assuming strips are wired common anode) or Bob's suggestion on the other thread.
6 10K
6 150R
Stripboard
Barrel connector for 12V input
4 2-way pcb screw terminals
What else? Some smoothing caps, a fuse?
What will you use as a power supply?
PaulRB:
Ok, so you are prototyping on breadboard first?Sugguested parts list (enyone feel free to chip in if I miss anything or suggest anything unsuitable):
6 irl520 (assuming strips are wired common anode) or Bob's suggestion on the other thread.
6 10K
6 150R
Stripboard
Barrel connector for 12V input
4 2-way pcb screw terminalsWhat else? Some smoothing caps, a fuse?
What will you use as a power supply?
A laptop 12V 6A power supply brick. Thats whats powering the strips right now, I need to insert Arduino/FETs in the path to make them dimmable.
Okay, so slight change of plan!
I think I am going to use a a PCA9685 driving IRF540 FETs with 6-8 independent power inputs and outputs.
That would free up the arduino and by making some completly independent, they can be anything from 5V-24V PWM channels.
If this works fine, I can do a daughter board to bringout the remaining 8 channels (its a 16 channel PWM IC).
This can then be used to drive LED strips, servo practically anything...
Basically http://www.ebay.com/itm/370899927156?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 but use beefier FETs and independent power inputs and outputs. Ditch the switches to make some space.
What do you guys think?
That sounds like a good plan. If you want to prototype this before committing to a custom PCB try this motor shield from Adafruit. Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface [PCA9685] : ID 815 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits
the PCA9685 used on the board is really an LED driver chip.
All the chips came in. First thing PCA9685 is TINY, I mean TINY! Plus its SMD and not DIP. I cant breadboard it! Crap!
That means I need to rush my PCB plans. Does someone have any ideas about how to breadboard a SMD chip? And that too tiny!
Just FYI, this is the adapter I ordered http://www.ebay.com/itm/121142761884?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
ordered a tssop28 to dip adapter from ebay. now i have to wait for it to come in before i can breadboard my circuit. i wish i had known that this thing is sooo tiny...i would have ordered the adapter earlier. oh well!
So I have one channel working on a breadboard. I am stress testing it leaving it on and looking at the temps and voltage draw to make sure nothing blows up!
I plan to put ethernet sheild and modify the bootloader to do tftp so that I can remotely upload new code and test it now that the setup is actually in the kitchen and not on my desk.
I think I found instructions on how to do that!
What about the serial port? I use putty on my desk when arduino is locally connected. Is there is a way to get the serial port output redirected to ethernet port short of using a terminal server !
Catching up on old thread/project here! Got distracted by other stuff!
Anywhoo! I have been able to breadboard the whole project and it seems to be working fine.
Next steps are:
Any ideas?
-AM
I have decided to do the 4 channel pcb first and then exapnd it with daughter boarda if needed. Found a place online that can fabricate the pcb for resonable price if its less than 5x5 cm, which i think it should be.
Plan to put up some pics soon!
-AM