Mario, I am to clarify what you (maybe) imagined some message ago. My idea is to drive a lot of DC motors using many L293D's (Half bridge motor driver). These need a PWM signal for speed (and other signals, that I would send with 74HC595's), so I thought to the combination with TLC5940, but I'm starting to fear this is a little at dream level... In each L293D signals would enter coming from these two chips. Do I have to change my ideas? Andrea

Hi, Mario, nice to hear from you again! :-) Yes, you are right, 'cumbersome', for the TLC5940 is the minimum :-) I've seen the ICs you mention, and they look promising: you can also order free samples, but I see that they are all in formats not much hobby-friendly (no DIP, just to be clear!). If it's really the case, I cannot understand how I could use them in my small, single, applications... Andrea

I'm looking for some examples (wiring diagram & code) on how to use this IC without any special function (just to start with setting PWM output values, no corrections, nothing).
There is already another thread, where I asked for info, http://forums.netdui...h__1#entry18925 but I see that it doesn't come up on the list (maybe it's too old), so I start a new thread here.
I found very difficult even only to understand the needed wiring, so a very very short mini-tutorial would be really appreciated (not only by me, I'm sure...).
Thanks in advance
Andrea

@nzc: why did you say vprg is not wired out? From the pictures and the schematic, it looks just right there! Andrea

@NZC I thank you really much, because at last I found my problem: one of the wires I use on my breadboard was partially broken, or better, could not make a right contact on the netduino. Since I saw that the led pulsed erratically, I started to change the wires one by one, and I found the faulty one. Once I changed it, everything was ok!!! :-(((((((((( If you didn't gave me all the indications to have a functioning solution (thanks to the schematic on sparkfun too!) I could never think to a faulty wire! :-) Andrea

Ok, since I didn't give up, and made again all the steps suggested in this, as in other, thread, I finally found (I must have made something wrong on the first trial) what the problem really is: NEVYN was totally right, in the high level limit for the 5VDC used as Vcc. The datasheet is clear, even if I didn't pay too much attention on this: the high level limit is 0.8 * Vcc, so Netduino pins cannot drive the signal high (Nevyn says 0.7, but I think he hadn't the datasheet just in front). When powered by a 3.3 signal, all is smooth and good, under any condition, so I think this is the right solution to have. My only remaining problem is now that some of the pins are always off, some are partially powered, and so on. Now, there are two alternatives... one is that the source code I'm using (by NZC) still has some bug :-))) (no critics, here: you've done a wonderful work!) OR there is some dot correction on the chip (but this looks a little improbable... I never gave it the 20more VCC to write it! Some other test will solve (I hope) the situation! :-) I'll prepare a Fritzing commented diagram for the solution... Andrea

Ok, it looks I have to excuse myself (again!) for the trouble I caused in this thread! :-( I finally found the *REAL* problem I'm having. One of the connectors of my Netduino is faulty ! :-((((((( The block from D8 to Aref is loose, in the sense that I put the wires inside, but it makes a strange contact (I suppose). I don't know how to explain it well in English, but if I put a finger on the wires, not on the connector itself, and push them left (or right, it's the same thing) the contact becomes perfect, and everything is ok (LEDs fade on and off really smoothly!). If only I relax the push (without even taking out the finger completely) and all becomes flashy and flickering. What do I have to do, in a case like this? First option is of course to throw it away, and buy another... but is there anything else to do? I don't think that desoldering it can be the right thing to do... Andrea

No, it's really stranger than what I said: if I use directly led+resistor, all is smooth and soft... when using the TLC5940 all changes... :-((( Mario was right, when he said that this is a very strange chip... :-((( I don't know what to do: I changed the breadboard, the wires, and the netduino is perfect, using for example a motor with an L293D, but when I use the TLC, I have to touch the wires, and not always it behaves well... :-( I have three of them, and all show this behaviour! Bewitched chip... I'm sure... :-) Andrea

Not that I know of... :-( Good night, and thank you again! Andrea

Hi Mark, and thanks for your help. It looks like I totally misunderstood the role of the GSCLK signal, so I have to study again the documentation... :-( To clarify my goals: I want to have many PWM outputs controlled by Netduino, so I thought that an SPI chain of TLC5940's could be ideal, but the chip has much more functionalities I don't need at all. What I would need is: set the PWM 12 to 40%, make something else for five seconds, then set PWM 8 to 80%, then after two seconds more, re-set the PWM 12 to 0%, and so on. Nothing to fade in real time, no corrections, no adjustments of any type. I think I would use only a fraction of the chip capabilities, but that's ok, for me. Only, it has to be simple, I (still) don't have much experience on electronics... Thanks again. Andrea

Hope this helps??? Sure it does! :-) So, for example, could you point me to some chainable ICs for multiplying PWMs? As of tonight, I still cannot even light a LED with your code, I think I'm missing something with the wiring, but I don't know why... Thanks any time! :-) Andrea

...for those that are not so experts, could we have a Fritzing schema to follow (or any equivalent mapping of the wires from Netduino to the TLC5940), NOT using an external GSCLK signal (not anyone wants to fade... maybe many want to be able to switch between different discrete predetermined levels). I googled and find many examples using arduino, without the GSCLK set, so I would like to know if there are very simple implementations using only netduino and the chip, how to connect them, and a minimal (hence simple) sample code... Am I asking too much? :-))) Thanks in advance to anyone available to help... Andrea

No problem at all! Rather, thank you for your interest! Andrea

Mario,
can you give a look at this thread?
http://www.avrfreaks...ewtopic&t=60979
It looks like leveraging low data frequencies, some result can be obtained.
I cannot understand the technical details, but someone agrees, some other not! :-)
Andrea

...and I would add this document, too...
http://www.ti.com/li...441/slyt441.pdf
It looks interesting.
Andrea

...oh, and for now, I didn't think at all to locos and motors... we will see: I'm sorry, but not being an expert, I prefer to think problem by problem... Andrea

Ok! :-) I realize, and I thank you, that you are all very kind. As for now, I think I have really *a lot* to study, and to test. My (little) spare time will go to this project, and I will report the progress here. I would have a lot more questions, but it would not be fair to ask everything, and not try and test, so I'll keep silent, now, and will start with the components I already ordered. Thanks to anyone, I'll let you know everything! Bye Andrea

Thanks very much, Paul, this is by far *much* more than what I hoped for. But I still have many questions, and I don't even hope for a further answer from you! :-) First of all, I need to clarify, for what I've seen of the model: rail exchange is done with a three-way pulse button, that closes a 16V AC circuit (this looks very strange to me! why not DC???) in one of two directions: you give an impulse up, for example, and the rail goes right, you give an impulse down, and you get the rail going left. There is an electromagnet calling the rail in the two directions. So the first problem is just this: googling around, I saw many people saying to *NOT* use DC to AC relay control, because of some coil *induction* effect (I don't know what this is, but they say that voltage can go really up for a few moments). Can you confirm that (I suppose because of the very small power) I will not have this kind of problem? The problem with the lights is much simpler: they are all very small LEDs, so the only problem, I think, is to use some sort of bus just to not have that many wires going all around. Actually for each LED there are two wires going back to the central control panel, and I think they are at least one hundred! A first approach could even be to use some other NetDuino in calculated places, to control local groups of leds, but then I have the problem of 'speaking' from a NetDuino to another, even if I think I can find documentation on this. The last problem, that in the first post I didn't mention, is to control train movement. Actually, since there are five distinct groups of binaries, my friend has five power supplies, but of a type I didn't know about. In Italy we have 220V AC, so this is the input, but then there are two outputs: one is the 16V AC to drive rail exchange, and one is the DC current to move trains, that can be altered with a gauge. Rotating this, you can even invert positive and negative, I suppose, because trains on the rails invert direction, and go faster or slower according to the level of rotation: so I suppose that this is some kind of potentiometer that can invert Voltage. My last question, at this point, is: may I think to replace this power supply with 'something' (what can it be?) that I can then control with software with a NetDuino? Right now, if you want to simulate the train going in station, you have to manually slow it with the gauge, but it would be fantastic to have some software algorithm at the press of a button, that slows the train until it stops! Too many problems? All of this looks very interesting, to me, even only to learn NetDuino programming *AND* basic electronics control (I already have bought a couple of books!). I am obviously available to share on this community all the details and the lessons learned! Thanks again. Andrea

In fact I'm thinking to go down the data rate to minimum speeds... I don't think this can be a problem, with what I need... If this helps me a lot, do you think the solution can become feasible again? Yes, you are right... the only thing is to make some tests... Andrea

Ok, I have still another order to do, for the relays! :-))) But, what's more interesting, today, is that I tried to use SPI on a long cable, so I create a test environment: My Netduino Plus, with two cables connected: one with two wires for +3.3VDC and Ground, and the other for the SPI signals (three wires used out of four). The cable was 5 meters long (16 feet?): I cheated a little bit, because I didn't have two different cables at hand, so I kept Netduino and breadbord very close each other, and used a normal short cable for +3.3 and ground, BUT I used the 5-meters long cable for the SPI. I started with a very conservative 1Khz setup (only because I couldn't make still less! :-)), and I found the signals went up and down without a single problem (leds attached, with fixed on/off time length). Then I went up until I saw that even at 1Mhz, the behaviour was still perfect, at least for what I could see personally on the leds (that's what's important to me). I don't know if at low level there are any problems, in syncing or what, and I know (thanks to Mario) that the main problem is not the frequency, but the wave shape: still, I'm very happy for the result, just for my start in this new (for me) field. Is there anyone that can tell me if I'm oversimplifying the problem? I know that I'll have to use it in a 'noisy' environment, but it looks like the start is encouraging! By the way, the cable I used for the SPI is a shielded telephone cable, with the mark on it: 'SYT PLUS 1 NUM 2X2XAWG24 A10-41/04', if someone knows what it can mean. I can only understand that they are 4 wires (NOT twisted, moreover) of type AWG24, plus another one, without any plastic around it. As always, I would like some comment from who knows way much more than me... :-) Andrea

@MrSmoofy: No, digital solutions are not an option, we already talked about this previously in this thread. Thanks anyway. @PaulNewton: Paul, you are always the man! :-) Every message of yours gives me enough sparks to think about, and learning (or remembering) something interesting. But: since I already tested with PWM to change speed, and I saw that Voltage and Amperes are different at each speed, if I turn the wheel with my fingers, or with another motor, I can only get the voltage (and Amperes) for that speed. I will never know if the wheel is at its maximum speed, or to the maximum 'normal' speed that I have to run it to! The question came to my mind just because I tried many motors, at different input voltages, and different PWMs, but I cannot know if I'm going to burn them soon! It's not a great problem, I think that in another two weeks I'll have more than 100 of them, but just to know and learn... :-) Andrea

Hi to everyone! :-) Here is the silly man again! :-))) Today's question is: since I asked my friends to find for me old car radios, printers, and whatever has a little motor in it, and now I have more than 30 small motors in my hands, all perfectly functioning (for my Christmas animated nativity), how can I find out what are their characteristics, first of all Voltage, since noone has anything written on it? Is it silly enough, for a question here? :-) Andrea

Did you spot the problem? - The Netduino only has 4 PWM outputs, so you might need to use a PWM shield to get enough PWM outputs for your 5 sets of rails.

Hi, Paul, since my first tests are ok, I'm now thinking again to the problem of loco controlling.
You told me about a pwm shield, I saw it, and I think it can be a good (and cheap!) solution. What I cannot understand is that to me it seems that I'm using in the shield the same PWM pins that I have on the Netduino, so I cannot reach the five PWM that I need.
Moreover, if I understand it well, I need TWO PWM pins to control a single loco? Forward/reverse? Please, can you give me some hint?
Andrea

Yes, I had already googled to find the same results (am I entitled to be called 'a wise man', too? :-)). What I was pointing out was that even if this is not the best cable I can use (it's another order of mine, still waiting for 100 meters of CAT5E FTP), I could easily obtain perfect results on a 5 meters cable (and at 1Mhz!), that, for what I was told here, wasn't expected... Andrea

Hi to everybody. As a software programmer, I have a very small knowledge (and all theoretical!) about hardware at this level. So, my problem is: a friend of mine has a very large train model set (five groups of rails, 15 trains, 10 meters by 3), all handled in analogical (kilometers of wires! :-)). So I told him I could help, trying to use a netduino to handle all the problems, but now I realize I don't have the necessary experience. So, just to start, I focused the first two problems: - Rail exchange is handled by a 16V AC line: to move the rail in one of two positions, you have to close one of the two circuits (ground is common), and just with an impulse. Which kind of relay/transistor do I have to use? - Traffic lights, rail exchange, other lights: all need wires, and on a 10x3 meters set, there are a lot of them. I'm thinking to some sort of bus (I2C?) to minimize the number of wires, but then, again, which kind of solution may I imagine? Theoretically, I would like to have some sort of I/O controller with for example 16 pins, and being able to connect to it from a distance of 5 meters, or something like that; from there, I would have to use way less wires... Anyone so kind to give me at least the directions where to look for? Thanks in advance to anyone, and excuse my poor English... Andrea