What is the best signal interface for PC ?

[marconi]

First off all, congratulation on the movie and showing the full working project. Very fascinating !!!
I still have to try it your way someday, in the future.
-to your question now: - Well, when a pin of the IC is floating , it is not 0V nor 5V. Right? But by having all those leds and resistors to 0V, I efectively put to 0V every IO pin of the chip. THus, not leaving anything really floating. This is important in code, when I am switching from Outputs to Inputs. By switching to Inputs is the programming way of 'floating' the Output. By inversing it. Its a trick learned when I was programming PIC's MCU's. But... having all these pins to 0V ---anyway--- , it doesnt matter if I was switching to Input or to Output in code, because the state was 0V anyway. So the speed was not affected but the entire logic of the code was affected, which is more important and more drastic. I hope is more clear now what I did there.

Thank you. I see what you mean. The same applies to the eeprom I used but in its case it did not do anything with the data at its input/output pins until they were selected as such and there was a 'read' signal pulse. I suppose the same applies to the MCP23017. I have not had the time nor inclination to fully understand how the 23017 operates and is used to offer any immediate advice. I remain sceptical though.

 

[_q12x_]

I have not had the time nor inclination to fully understand how the 23017 operates

Dont worry about that. That is my concern.
Some good news. I went to arduino forums and put this entire project we discussed here in their hands to help me make the speed of the led matrix to be faster from the code perspective ofcourse. And the good news is, that I really made it faster than in the very beginning. Its not as fast as yours, it is still flickering but the fv is visible much higher than before. I have tested 2 libraries for coding this MCP through arduino IDE and this eat me some time to concentrate, evaluate, mostly guess and test hundreds of permutations. But it worked, now is considerably faster, because some special functions I learned to use.
I am asking you to make me a circuit drawing of what you just made there. But make it clear enough for me, not a scribbled wire of lines. Make it look good. Like made for me. Thank you. Because I want to try your way as well.
- Oh, and I just changed all the 1.1k resistors with 300R resistors now. Is not full brightness of the led but is a bit more visible than with 1.1k which in daylight was almost invisible, and only in shadow was starting to show its led light. Speaking from the speed of the last program I made last. The leds are dimming as long as the fv/speed is increasing. Especially much more lower visibility on a single full line or full column..

 

[marconi]

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[marconi]

One of the reasons I like working with you is that you are motivated by and enjoy learning from you own experience and trials. And I think you should by now realise that these days my practical work records ‘work in progress’ accompanied by scraps of paper with electrical art on it. I will not therefore and alas and to your disappointment perhaps be producing blueprints to your exquisite standard to follow. We plough our own furrows. At 61 I simply cannot be bothered with the formality after a lifetime of it.

 

[_q12x_]

At least enumerate all the IC's you used and for what purpose if possible and I will do the circuit myself if I will be able to. At least I will give it a try using Proteus simulator.

 

[marconi]

Make a 555 clock running at 1Hz
Connect this clock to a 4 bit counter such as a 7493. The 7493 is ideal because as you know it has integral reset logic.
Wire the 7493 to its reset pins so that it counts in binary 0000 to 0100 - these are the five states to control the scanning of the columns.
Connect the Q outputs of the 7493 to a 74138 to turn the binary sequence into a one-of-five word sequence ie 00001, 00010, 00100.....

Working of 74138 decoder IC - https://www.tutorialspoint.com/working-of-74138-decoder-ic

Use the five bit word to turn on in turn the column transistors Cn I showed in my earlier electrical art. The five Cn transistors must be able to pass a collector current of 7 x one LED current. Base resistor of say 22kR - but I will check this later.

Connect 7 transistors as in my earlier electrical art to the 7 row/lines of the 7 x 5 display with suitable collector and base resistors. I used 1kR and 22kR respectively - but will check later. These transistors only carry the current of one LED.

Connect seven fly leads to the base resistors of the row/line transistors so that you can set up a column pattern by connecting to 5V or 0V 0000000 to turn all column LEDs on and 1111111 to turn all off. The row line transistors switches are negative logic ie active low.

 

[_q12x_]

Ok, thanks mister @marconi , this should be good enough to make the circuit in my simulator.

 

[_q12x_]

I have a slight bad luck that was giving signs for some time but last night I felt it very easy to bent and this is sign it's the last bent will have. If I try to straighten it back again, like I did it a couple times before, in time, it will break for good. So I am taking measures now to make a new one from the scraps I have. That new pointer is actually a brand new one (from ebay) that I cut it into my lathe to try fitting it into this iron body I have. But... its a failure and I could not fit it as the original was. SO now I have to build from ground a new head, using this already busted copper head, but brand new and unused. Whish me luck because I want to finish it at least in 1 day.

 

[marconi]

Just remembered that you will need to invert the 74138 outputs because they are active low. Its output sequence is of the form 11110, 11101, 11011, 10111, 01111.

 

[_q12x_]

Luckily it took me about ~2h to make a new modality of contact for my new heat Iron tip. A new press fitting head that is full iron instead of copper. Only the tip is copper. I test it already and I have to dial to maximum for it to heat up quickly enough. But it works. Yay.... very happy, is stable and working.
I will soon start building the simulation for your circuit.

 

[marconi]

London calling - what news from Romania please? I would like to see you spell out 'Romania' or your name or moniker on the 7x5.

 

[_q12x_]

I was quite busy actually, I had to repair the tip of my iron soldering, I had to make a movie with all the progress I did so far on the led matrix code speed, in arduino and its library functions, and only from this point forward I can concentrate on the simulation. I did some research to figure out how to simulate RAM chips in proteus, because is not simple, and I did find a solution and I have to test it out. I will update you soon. Remember that for you is easy because you have experience with these things, but for me is the first time (for some part of it) thats why it takes awhile.
And I already buy your 74LS138 Decoder/Demultiplexer IC..from aliexpres. It will arrive in maximum 2 months (if im lucky).

 

[_q12x_]

 

[marconi]

Brilliant work! Your earlier hesitancy was unfounded. As I suspected, you pick things up quickly.

Next step is to use the ROM to store the five 7 bit words which describe the fonts of the alphanumerics you want to use.

I used this as my font reference but you could design your own perhaps:

5x7 DOT Matrix - https://fontstruct.com/fontstructions/show/847768/5x7_dot_matrix

I have two eeproms left - would you like me to send you one?

http://cva.stanford.edu/classes/cs99s/datasheets/at28c16.pdf

PS1: LED current limiting resistors?
PS2: Base resistors for 7 x Row transistors?
PS3: Base resistors for 5 x Column transistors?

 

[marconi]

q12X My next project is the modernise and make more reliable the remotely controlled door lock my wife uses to let her nurses and cleaning ladies in each day. I bought over a year ago(! - I lack your motivation) some RF Solutions radio frequency key fobs and receivers boards which I need to turn into a working system. I think it was these items - need too search them out.

BRAVO-T 8 CHANNEL TRANSCEIVER TELEMETRY MODULE 1000M - https://www.rfsolutions.co.uk/radio-modules-c10/bravo-t-8-channel-transceiver-telemetry-module-1000m-p378

FOBBER 1 CHANNEL ON/OFF BUTTON, UP TO 200M, 868MHz KEY FOB TRANSMITTER - https://www.rfsolutions.co.uk/remote-control-systems-c9/fobber-key-fobs-transmitter-c204/fobber-868mhz-key-fob-c206/fobber-1-channel-on-off-button-up-to-200m-868mhz-key-fob-transmitter-p760

 

[_q12x_]

hello mister @marconi,
I still can not see a way to create any shape/character on this matrix display.
Can you detail more from here? I really dont see it. As I mentioned in the movie as well.

Brilliant work! Your earlier hesitancy was unfounded. As I suspected, you pick things up quickly.

Im still hesitant at this moment as well. I pick things if I can follow a logic. But right now is 0 in my mind.

I have two eeproms left - would you like me to send you one?

Yes. But please dont make a BIG box for it, since these mail monkeys here in my town, are looking directly to the size of the package, and then to it's weight. And they tax plentifully if is over-sized or over-weight. My suggestion and please do exactly as Im telling you, put this IC into a simple envelope, the smaller the better. Like this is perfect : (trust me)

Don't even think to put into a colored envelope because that is also "too fancy" and the monkeys here, also tax the hell out of me. Also from your perspective you will pay something like 1 pound or close to it. I didnt check out how UK are taxing small envelope mail delivery. It might be free for you. Who knows. But I guarantee it will be very cheap. It will be as you are sending me an old fashion card in an envelope.
You most probably will have to bent OUTSIDE the legs of the IC , to be in line with the IC and not to poke the envelope paper if left unbent. You can also put some cardboard on the pins , poke the pointy legs into a small, cut to size cardboard, for a small increased protection.

I will resend you my mail address in private.
And thank you for it ! You are very cool.

I bought over a year ago(! - I lack your motivation) some RF Solutions radio frequency key fobs and receivers boards which I need to turn into a working system. I think it was these items - need too search them out.

Well, look on them and BE SURE are these devices from your links. And not some other brand or #id.
Do it now.
On the link page you give me, I find a video presentation on youtube:

They are describing this RF board very well, in a clear UK accent, haha, and they seem exceptionally easy to implement. They show the pin diagram connections to +3V and 0V for both MODES of this board that can be a receiver OR a transmitter depends how you wire those pins. VERY easy and straight forward. It appears that has a LEARNING button on the receiver side. So you might be very much in luck to press that learning button, press your remote button, and wait for it to learn the signal, and thats it, that simple. After that will 'recognise' your specific RF from that little remote. You can play with other RF transmitting devices. Your TV remote is transmitting in infrared so it will not work(unless this board has an IR receiver as well), and it is directional anyway and limited range. So it might be RF only what you have there.
I find this board datasheet >>> https://docs.rs-online.com/6486/0900766b813bbdc3.pdf
- Read it -
And I made for you it's pin connections more clear to follow

This board works at 3V, designed to be supplied from a 2x1.5V batteries (as a transmitter) but also as a receiver, same power supply.

So, in your case, I will use a transformer, even a mobile charger will be fine at 12V, 9V, 5V, whatever. Also >500mA. Like this one:

then a variable voltage regulator like LM317 or AMS1117(smd), and wire it for 3V output and power your Receiver board (in your case).
This is how I would do it. VERY SIMPLE project !!! You can make it in 1 day, top to bottom.
Also I want pictures and movie with it installed and working until tomorrow morning !

 

[_q12x_]

Ive just made a test right now and you may have to put some sewing thread/string on top because these small cardboards may fly on vibration. If you secure them with a piece of sewing string it should be more than fine. Here are my test pictures:

 

[marconi]

We both have a 555 clock. I thought you might like to see my 7x5 when I reduce my clock to 1 Hz for a while and then return it to 1kHz. You can see how the column leds change to construct the letter A and what the eye and brain observed when the clock rate is increased.

 

[_q12x_]

I still can not see a way to create any shape/character on this matrix display with the circuit I have so far.
Can you detail more from here? I really dont see it. As I mentioned in the movie as well.

 

[marconi]

If you had five 7 bit memory locations which you could address/read using the 3 bit code the 7493 generates as it counts in binary from 0000 to 0100 then you can use this scheme to select a 7 bit memory location which contains the data to turn on the required leds in a column, column by column as my video shows. Then you speed it up.

What I would like you to see for yourself is how much in the design of digital electronics is about stringing/sequencing many very simple elemental actions/processes very quickly to generate what is wanted.