I'm in the beginning of a small project here where I need to control a 10x11 matrix of LEDs driven by 12V. I already have all the LEDs so I'm just searching around for the best solution in howto address these.
The thing is that on each dot, there is actually 3 LEDs, as they are cut from a LED-strip.
I have successfully made a setup where I can control the brightness of the LEDs using a MOSFET and a opto resistor, i.e. depending on the brightness in the room the brightness of the LEDS is adjusted.
Next thing that came to mind on howto control each individual dot on the matrix was to use 74HC595 and ULN2803, since there are 110 spots on the matrix I figured that I would need quite a lot of these chips in order to cover them all.
Then googling some more, I found the HT1632 driver which would in theory do a lot of work for me. However then it comes to voltage and power through that one given the specs on my LEDs. Thus I don't think it is possible to directly use this chip. Would it be possible to use the HT-chip together with the ULN2803 in some way in order to increase the voltage on the LEDs?
Or am I just out in space with that assumption?
If it doesn't work, then would multiplexing be something that could be used here? I.e. using some shift registers and the transistor arrays but just a handful of them in order to drive the LEDs?
The strip I'm using does not include a driver that enables me to directly from the Arduino control it. It is not possible to address the individual LEDs on this strip also the distance between the light spots on the LED is way to narrow for my application.
As I stated in the first post, I have successfully managed to control a bunch of strip parts (i.e. 10 strips with three LEDs in each) The problem is to individually turn these groups by three on and off. And I know this is doable using a bunch of shift registers and a transistor array such as ULN2083. I was however interested in if it is possible to do it using the HT1632 to control the input to the transistors and thus drive the LEDs.
I suppose you want the HT1632 because of its PWM capability.
Unfortunately, it is a 5V matrix driver, so it cannot control 12V LED pieces (which I understand consist of three series LEDs plus one resistor each) without a "high side driver" consisting of a NPN and PNP transistor with two resistors for each row.
I'm revisiting my project again, sorry for not answering sooner.
Made some experiments and figured out to control the "low" side using a npn transistor for the columns in my matrix. I have seen an example which states to be using npn-transistors to control both low and the high side, however this works for 5V LEDs it does not using my current transistors work with the 12V LEDs.
I have just placed an order for a bunch of transistors with various values including PNP. I have though a little bad feeling that it won't do much good i.e. that I can't use the 5V of the arduino to control the base on the PNP to be able to switch the 12V "high" side of the LEDs.
Hopefully someone understands my dilemma and can point me in some direction. The last resort would be to limit my solution to not use multiplexing and thus not being able to control each individual point in the matrix. That would work but will not be at all as cool as have a full fledged matrix.
Note also! I have dropped the use of the HT1632, currently I'm just using the 74hc595 and ULN2803 and some single transistors.
So you mean that it is possible to directly connect 12V as vcc to that IC and have it control the LEDs as if I were to use 5V LEDs and only the 74hc595?
Vcc to the TPIC6B595 is still 5V, and it is controlled directly from the Arduino (like a 74HC595).
Its outputs are open-drain but unlike the ULN2803, can pull very close to ground, and rated for a significant voltage - 50 V - and current - 150 mA.
That means you can use one to directly drive the LED cathodes, and another to switch the base resistors of the PNP transistors whose emitters are connected to the 12 to 15 V and collectors connected to the LED anodes. You still require the current control resistors in the LED cathodes if you drive one anode row at a time (or vice versa).