[moved] Help building device with Keypad, Lights and Buzzer

[momo2000]

It has been since I was a kid since I built & soldered things, but need to build 5 of these devices for a “simulation” so I’m trying to figure out where to start and am looking for suggestions. I went to the business school, not the engineering school! Is there a project that is somewhat like this that I could modify, do I buy a project book, is it simple enough that someone would give me some direction? Here is what I am trying to build (see uploaded crude diagram of my thinking on the circuit/components):

SUMMARY: Keypad that when you enter the correct 4 digit code (and probably #) it turns the red light OFF and green light ON.

SPECIFICS:
Green light turns on when power applied and is in “ready state/disarmed” (Optionally all lights could be off)

Keypad/IC that can be programmed with a 4 digit code. Code must remain when power fails.

Single push of the momentary switch, “arms” the circuit. Meaning that #1. The red light turns on, and the buzzer sounds for a few seconds.

When you enter the correct 4 digit code, the circuit goes back to “ready state/disarmed” meaning that #1. The red light turns off, and the green light turns on.

Device now back in “ready state”, momentary switch could be pushed and system “armed” again (or in rare occasions, the 4 digit code could be changed).

The 2-light/buzzer combo unit [that I must use] is 24VDC, so not sure if I can run that directly from the board/IC or will have to use a relay. Running directly from the board is MUCH PREFERRED. This 24VDC 2-light/buzzer combo unit is the only part that is already determined. All other parts are flexible.

Need to put the IC/Board/Switch in a project box.

Of course cheap, reliable, and easy for an amateur to build



- - - Updated - - -

OK, been doing more thinking. I have a Arduino Lenardo that I bought a year ago, but never did anything with. Just pulled it out and started with the basic examples. Maybe this would be a good platform for this project? Thoughts or guidance on this strategy of using this board for this project, good/bad idea?

 

[D.A.(Tony)Stewart]

you mean like this https://www.amazon.com/s?rh=n:573765011,p_n_feature_keywords_browse-bin:2797305011 ?

Yes an Arduino is a good idea but expensive for time.

 

[BradtheRad]

The keypad switches are probably arranged something like this diagram:

Expect this to tie up 8 input pins on your IC, to keep things simple.

The unlocking combination is stored in your IC's memory.

 

[Venkadesh_M]

Seems a good thing for beginner, If you want to change a password then you will need EEPROM memory In the controller or eternally.

 

[horace1]

for undergraduate and postgraduate student projects we find Microchip's microstick II useful
https://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=DM330013-2

if has an onboard programmer, choice of processors (PIC24FJ, PIC24E, PIC24H, dsPIC33, and PIC32) and a header to plug into a breadboard for you own circuits - it is low cost so if students wreck it we can throw it away!
once a prototype is implemented and tested students can then make their own PCB etc

 

[betwixt]

For cheapness and simplicity I would use a PIC16 processor. It will only need a small amount of program memory and a few bytes of EEPROM, something like a 16F628A can do it easily for very low cost.

Momo2000, you have done the correct first stages of development by specifying exactly what you want to achieve. It's suprising how many people start off with some parts then try to find something to do with them! Your next task is to work out which resources you need, for example, how many processor pins do you need to hook the keypad, lights and buzzer up. From that you can choose the most appropriate processor to use. You also need to consider the power requirement of the lights/buzzer box. You will not find a micro that can handle 24V directly but it is easy to use transistor drivers to operate the lights and buzzer. I wouldn't use relays, they are far more expensive, physically bigger and quite likely will still need transistors to drive them anyway. A single transistor for each indicator should be sufficient.

Brian.

 

[momo2000]

Yes, like a garage door opener, but that does a bit more.

 

[D.A.(Tony)Stewart]

Some of those garage door openers also open electric house doors , lights etc

they have more than one button.

 

[momo2000]

Thanks all. I've done some more research and decided to go the Arduino route. A bit more expensive, but I can make adjustments. Thanks for all your suggestions and advise.