I've created a small circuit on a couple of breadboards, with a 12 key keypad. The 7-segment LEDs consist of one 2-digit and one 4-didgit items. Each LED is connected (although not shown in breadboard diagram), to the MAX7219; D0 and D1 are connected to the 2-digit LED and D2, D3, D4 and D5 are connected to the 4-digit LED.
I've successfully checked that the OneWireKeypad works independently of the MAX7219 and 7-segment LEDs. Plus successfully checked that the MAX7219 and 7-segment LEDs work.
The problem I have is that when I link the two together via the V++ and Gnd rails, I can't get the keyboard to function. My program is fine (I'm a professional C++ Software Engineer), but I suspect that the power between the two needs some further components? Could someone please advise me how I can get the two to work as a single circuit?
This is the schematic view of the whole circuit. I have a 2-digit 7-seg LED & 4-digit 7-seg LED, but this doesn't affect the schematic.
I suspect I need a resistor between the Vcc from 5V of Arduino to R5? I would appreciate if someone could explain what I need to do to correct the issue. At the moment when I press any key on the keypad, the program reads it as Key: 1. When I have a keyboard circuit running on it's own the program correctly reads the key presses.
Sorry, my fault. Problem was due to me, one of the breadboards I'm using has a split rail and so the power wasn't connected between the two breadboards, as I did have them connected but at the far right. I feel so stupid.
This is why we ask to see a picture of your wiring.
Just looking at a schematic tells us very little as new people often have wiring errors due to unfamiliarity.
I'll bet this will not happen again.
Always check your circuit voltages with a volt meter
LarryD:
This is why we ask to see a picture of your wiring.
Just looking at a schematic tells us very little as new people often have wiring errors due to unfamiliarity.
I'll bet this will not happen again.
Always check your circuit voltages with a volt meter
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Point taken. I'll need to get a digital multi-meter very soon. Can anyone recommend a good one for a hobyist?
I still have the problem of the program not recognising the correct key presses every-time. Sometimes it will recognise the correct key and sometimes not, it appears to be the keys on the bottom row, i.e. '*', '0', and '#'. I would appreciate if someone could advise how to resolve this please?
Here's 3 photos of the project at the moment. Whole project:
closeup of the 1k ohm resistors for OnewireKeypad:
closeup of the 4.7k ohm resistors for OnewireKeypad:
This could imply you need to adjust your ranges, or there is noise on the power rails, or the supply is changing due to load changes.
Add some more decoupling.
If you have an external 5V power supply, use it to power the display section.
LarryD:
This could imply you need to adjust your ranges, or there is noise on the power rails, or the supply is changing due to load changes.
Add some more decoupling.
If you have an external 5V power supply, use it to power the display section.
The way you have it in your schematic isn't the same as how you have it wired up!
I've connected the external power to the display section, and running the keyboard off of the Arduino. I found that I still needed to connect Gnd from the keyboard section to the display section. Is that correct?
What do you mean by "The way you have it in your schematic isn't the same as how you have it wired up!" ? I'm open to advice.
I've connected the external power to the display section, and running the keyboard off of the Arduino. I found that I still needed to connect Gnd from the keyboard section to the display section. Is that correct?
Absolutely.
What do you mean by "The way you have it in your schematic isn't the same as how you have it wired up!" ? I'm open to advice.
This is just my user tag. It is something that new users often fall into. Not directed at you
AndyInSurrey:
Point taken. I'll need to get a digital multi-meter very soon. Can anyone recommend a good one for a hobbyist?
Just for starters, a $5 one will do just fine .
In fact, buy three (or more) of them, keep one in your car (and ...) - that's the sign of a serious "techie".
You may at some stage need a more sophisticate one, but need not worry now. One of the most important features is in fact, "auto off" to prevent you from accidentally and frequently flattening batteries.
I am impressed that you properly link good photos in your posts, rather than the thoroughly fouled-up "attachments" for which this forum software is configured.
Another frequent source of misbehaviour is faulty jumper wires. You can test them by chaining them all together on a breadboard and connecting a LED and resistor in series with 5V. If they work, OK, but if they do not, just keep dividing the chain in halves until you find the faulty one(s).
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