Hello everyone. I am obviously new here and I was uncertain whether to post such vague questions, but the description for this particular category is "Advice on general approaches or feasibility" and that is exactly what I need.
First, I would like to provide a little background about me and the project I am trying to complete. Last fall, I had the brilliant idea of making a DIY laser maze for the kids. I basically have/had no electronic background so I depended on what I could find online and an incredibly helpful forum (not here, but more on that later).
After starting with a simple 555 IC, I eventually came up with a circuit using a quad op-amp IC. From the beginning, I was just using LDR's. I had some luck getting a "prototype" course set-up up in our extra room so I had moved on to a separate part of the project - tracking the number of times the kids hit the laser(s).
I also coach youth wrestling and once the season started all progress on this project came to a screeching halt.
Fast forward to a few weeks ago (wrestling is over, time to get back on the horse) and I quickly found out anything I thought I "learned" last fall must have been in short term memory. It was a bit frustrating trying to get back up to speed and I found myself searching the net for guidance.
Well, at some point during my searching I found some videos on the Arduino and my brain has not stopped since. I think/hope I can learn enough of the basics to have a pretty awesome setup. So please keep in mind my background/lack of programming(or even electronics) has I try to layout my plan and ask for your feedback.
I would like to have 12 laser/LDR circuits (simple voltage divider feeding into analog pins). I would "dial" in the sensitivity on the programming side. (I have played with a tutorial I found online already.)
If/when an LDR goes dark, the corresponding laser would shut off for approx. 2 seconds, then be turned back on.
I would like to have three levels (easy, medium, ninja) that would be determine by which PB was pressed at the start.
I am assuming I will need some delay between when the lasers/LDR's are powered up and when the program checks the corresponding analog pin.
Even before I became aware of the arduino world, I had planned to have each "LDR/laser trip" trigger a small 3 digit LED display to keep track of the number of strikes. I also had a large 5" LED display planned for the overall time. (Most of the fancy pants mazes in malls have "penalty time" added directly to the overall time).
And the final item I hope to add in is a "siren"/noise maker whenever a laser is tripped. It would play for 4-5 sec. maybe, then shutoff.
I have added a drawing for the laser/LDR portion and would like some opinions on any show stopping issues with my overall intent. I have many questions regarding what can be/can not be done with the Arduino, so I figured I would put my concerns/question below.
1. One of my main concerns is not burning the arduino up. I have tested the lasers and each one draws about 25 mA @ 3V. I have an external power supply of 5V - 4A for the lasers, but I am not sure how to ensure the arduino does not see more current than it can handle. I know/think my circuit is missing resistors around each transistor, but I wanted to get my general concept out here so if there are major issues I can get on the right track. Will the use of transistors work to power the laser/LDR circuits and still keep the arduino safe?
2. I have succeeded in getting a 5" LED display working. The 5" displays are actually powered by a 20V supply, while the "main" portion of the circuit is powered with a 9V supply. Currently, the "time" part is just coming from a 555 circuit I found online that triggers every second. The official circuit has a crystal/timer IC portion, but I have not incorporated that yet. So, would it be possible to use the 9V supply from this circuit to power the arduino? Could I start/stop the time with it? And, the best case scenario, could I eliminate my small 1" strike counter and somehow add the time via the programming side? If I can't eliminate, can I use the arduino to count the strikes?
3. My last "hope" is to be able to have some sort of siren. Again, my concern is doing something wrong and burning up the board. The siren I salvaged from our old short bus runs approx. 31mA @ 12V. Yes, another, separate power supply.
I apologize for the novel right out of the gate. I would appreciate any feedback on flaws in the concept/plan I have. Please remember I have very little electronics background and zero programming. I have spent the last 2 days taking pages of notes on what I think I will need to do on the programming side. I was even going to try to start a sketch, but I did not want to invest the time upfront if I am hunting an incorrect path.
Thank you in advance for any guidance you may give - and Happy Father's Day to all the Dad's on here!