Using a TFT screen to read speed from a laser chrono

[Nominated]

Hi.
New at this but getting there.

Timing a school project - my CO2 powered car (like this Shop Pitsco | Dragsters )

I have written a code (well..copied and edited) that will measure a drop in reading on a LDR from a laser as my dragster moves through the beam, starts a timer and then stops time when a second laser is crossed 100mm away.
The code calculates the speed (average) over the 100mm.
I am using 2 analog inputs for the LDRs to read from. Works well using the Print Monitor.

I would like to place this onto a track and have a tft screen print out the speed.

I have purchased the following equipment:
2.4inch TFT
3.5inch TFT

Both fit straight onto the Uno without any wiring. Only problem is there is only 1 analogue channel left when the TFT shield is on. Can I use one of the TFT pins for my 2nd LDR input?

I have also purchased the Uno, mega and due. Hoping one of these will work (hopefully the Uno with the 3.5tft screen as preference)

I have been looking at writing code to make a simple 2 line read out - "Dragster Speed is... XXX KPH".

I would appreciate any help as the tutorials and help guides on these TFT's is confusing. I am a going crazy! They are very complicated and I want something simple.

I would be happy to donate $20 to your chose charity / arduino organisation if you can help. (I will place a screenshot of receipt). I have already spent too many nights stressing while looking for code to use -simple for some but impossible for me.

Current code (which prints to a serial monitor currently) below. Would love to know how to make this print out on a 2.4 or 3.5 inch screen.

I have attached pictures of my 'basic' set up.

int firstsens = 4;
int secondsens = 5;
unsigned long time, time2;
float kph, elap;
int val;
int val2;

void setup()
{
Serial.begin(9600);
pinMode (firstsens, INPUT);
pinMode (secondsens, INPUT);
}
void loop()

{
Serial.println("Waiting for Co2 car to launch....");
val = analogRead(firstsens);
val2 = analogRead(secondsens);
while (val > 200)
{
val = analogRead(firstsens);
}

while (val <= 200)
{
time = micros();
val = analogRead(firstsens);
}

while (val2 > 200)
{
val2 = analogRead(secondsens);
}

while (val2 <= 200)
{
time2 = micros();
val2 = analogRead(secondsens);
}
elap = time2 - time;

kph = (elap*1000)6060;
Serial.print(kph );
Serial.println (" kph");
}

[system]

Using a TFT screen to read speed from a laser chrono

Do you REALLY think you can do that? Displaying the speed on a TFT that the Arduino computed is a different story.

val = analogRead(firstsens);
val2 = analogRead(secondsens);
while (val > 200)
{
  val = analogRead(firstsens);
}

If you are going to wait for the analog reading from the first sensor to exceed some value, what was the point in reading the other one?

while (val <= 200)
{
time = micros();
val = analogRead(firstsens);
}

Why are you then waiting for the reading to drop?

I started to say that you have everything but the kitchen sink in the first picture, but wait, you do have a kitchen sink in the picture.

What kind of receiver are you using? An analog sensor is far to slow for what you are trying to measure.

[Nominated]

Thanks for getting back to me so fast!

Yeah, kitchen sink. Getting desperate. Trying it all.

I have 5v laser that aims directly at a LDR. Reading is over 900 but when a car goes through and breaks the beam the sensor value drops to 100 (ish).

Is the LDR is an analogue receiver??? Could I use a faster one (digital??? and what type of digital thingy?)

Code works so far. I modified it from a youtube paint ball chrono video. He used infra-red lcd and receiver. My gap is larger than the 20mm he used, so I swapped in a laser and LDR.

Am I on the right track or should I try another method??????

[system]

Is the LDR is an analogue receiver?

Yes, a light-dependent resistor is an analog device.

Could I use a faster one

Yes, there are phototransistors that are orders of magnitude faster.

Am I on the right track

I don't think so.

[Nominated]

ok.
I have Photo transistors and Infra-red LED's.
Will they work across a 200mm gap?

Any tips on getting the time to print out on a 3.5 inch TFT? or should I stick to a 2 LCD display.

[Nominated]

well,

PaulS - your response "I don't thinks so we neither helpful or useful".
I comprehend that it's not always possible for the experts to assist, I understand when you are stepping beyond your limit.
Next time a "sorry mate, can't help you" would have been more useful and honest.

So....

I got this thing working. Spits out the time onto a TFT 3.5 inch screen. Using 2x lasers and 2x LDR's.

I will upload a photo / video in the next 24 hours.

[Nominated]

3 photos

1. before car goes through lazers
2. while car is in the lazer timing zone
3. speed print out.

Guess i do have an Idea PaulS.
Thanks for helping.