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Topic: asking for help by anyone that wants a challenge :) (Read 1 time) previous topic - next topic


Hi guys, i was looking for some help from some more experienced people as im hopeless with electronics, im just gonna shout out what im aiming to do, hopefully someone will take the challenge to help me get my head around it (or at least point me in the right direction)

what i am trying to build is a relay controller with an LCD screen and LED's to show you whats activated and whats not...

it's for the dash of my race buggy/sand rail (an Edge Barracuda)

i need a large backlit LCD screen to display the status of a few things..

Door (reed switch)
Relay which is wired up to my modified Go-Pro Helmet camera to record all the carnage.
starter relay
(maybe a engine temp sensor would be handy too)

so basically, i want five buttons on the dash, with status LED's just above them...so, when you turn the ignition on they're red, and that specific button is pressed, it turns green.

obviously when i press the lights button, i want them to stay on, and when i press the button again, it turns them off.
but when i press the starter button, it will only stay on for the same time that i'm pressing it.

the five buttons need to be...

Lights (push-on, push-off)      12v 240mA
Door Latch(momentary)         12v 400mA
Camera(push-on, push-off)     12v 350mA
Starter(momentary)               12v 240mA
Fans (push-on, push-off)         12v 240mA

thats about it, i have no idea where to even start, ANY help at all would be much appreciated, thanks.

my Email address is shaneo_0306@hotmail.com


it's for the dash of my race buggy/sand rail (an Edge Barracuda)

i need a large backlit LCD screen to display the status of a few things..

Door (reed switch)

Your sand rail has doors?


haha, nah the top hatch part opens, allowing you to climb in and out via the roof. instead of taking the nets down all the time.
you pull it down and it locks in place and when you open it, a solenoid pulls a pin and the door/hatch opens with two small gas struts.


Controlling the LEDs appears to be a simple logic problem, you need an input from the ignition, one for each button/led and two outputs for each bicolour LED.

Does the starter button exist, or is this part of the project? IE you want the Arduino to start the motor?

Starter(momentary)               12v 240mA

OK I see this. 240mA for a starter, even for a starter solenoid that seems small?

All the other stuff is just a few IOs and/or transistors/relays. The fan RPM will need some thought, probably a photo interruptor setup or a hall effect sensor. It depends partly on the physical layout of the fan and housing.

I'd look into a decent power supply as well, one designed for a rugged environment.

You can get serial LCDs which will make the hardware a little simpler.


Rob Gray aka the GRAYnomad www.robgray.com


OK I see this. 240mA for a starter, even for a starter solenoid that seems small?

Likely that's for a smaller 12V SPST "Bosch" style automotive relay to trigger the larger starter relay/contactor/solenoid (whatever you want to call it)...
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.


yes cr0sh you're right, it's simply a small relay to throw a larger one.

and Graynomand, with the fan, it has an RPM sensor wire just like a PC fan, i made the people building my radiator order one from japan when it was getting built.


This looks like a good option for your project
If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

Ran Talbott

Two things you need to worry about for a sandrail display are daylight performance and resistance to environmental stress (heat, shock, and vibration).

The folks involved in the MPGuino project probably have some sage advice about which LCDs have worked well/poorly in cars.  They usually use 2x16 character displays, but you could use 2 of them,  with the "big numbers" software people have posted on the forum,  to give you bigger digital readouts.

As long as you're putting a micro in the system, you should consider programming it to do something attention-getting (like flashing the backlight, or a "Check the gauges, Dude!" LED) when the parameters you're measuring are out of their "safe" ranges.

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