JVDE

Hey guys!

I'm new on this forum.

I want to build a little something for my car.

A small, maybee 4 lines, alphanumeric LCD

that reads the following things:

• Outside temperature
• Inside temperature
• Battery voltage

But where do I start?

I found this LCD on internet:
http://www.quasarelectronics.com/cec014.htm

but it only can show programmed messages, so it can not make calculations. Like if I send 1 temperature value in by using 4 bits, it will not be able to calculate it...

what do I need?
I really want it to be standalone, don't need a PC in my car.

thnx!!

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shotgunefx

There are a ton of serial and USB LCDs and VFD Displays out there, you just need to get one and a program to drive them.

http://lcdsmartie.sourceforge.net/ is one, there dozens of others.

Matrix Orbital has a ton of displays.
http://www.matrixorbital.com/

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JVDE

thnx shotgun!

But as far as I can see these lcd's need a pc that constantly is connected??

Sorry if I'm wrong.

I want it to be standalone to build in my car dinslot.

thnx!

shotgunefx

Ah, well if that's the case, you're going to need "something" to drive the display like a microcontroller (aka MCU). You could use a PIC (or PICAXE, AVR, etc, whatever you find easier), if you're not inclined, those can take a bit of work, though they are cheap.

Maybe you want to take a look at Basic Stamps, which are basically PIC microcontrollers running a version of basic, so they are easy to program, but relatively expensive.

For the temperature, you can look at some Dallas 1-wire temperature sensors, pretty cheap ($3?) for the inside and out, tons of code on the net for all kinds of MCUs to, as far as measuring the voltage, not sure.

I'm no electrical whiz, but most PICs (and many other mcus) have an ADC (or a few) for measuring voltage, but ADCs measure voltage relative to what's called a "reference" voltage, which is usually whatever the microchip takes or less (~5v), so the car voltage is always going to be higher than that reference, so you can't measure it directly with the built in ADCs.

You could probably "scale" the voltage down with a voltage divider before feeding it to the ADC so you can measure the battery accurately relative to the regulated 5v in. I'm sure there's a better way to do it, but....

Basically, with MCUs, the lower level you get, the cheaper it is. A PIC (depending on what kind) can run as cheap as a dollar or two, and for what your trying to do, it's not a lot. A programmer can be had for $15 and up, then you just need a power supply for the 5v and a board.

You might want to check out Sparkfun which has a ton of development boards and parts.

If you are going to go the "PIC" route, you might want to buy (or checkout at your library) Programming Robotic Controllers by Myke Predko, gives a good overview of working with the PIC 16 series, also has sample code for driving an LCD, and interfacing to 1-wire sensors IIRC, so you'd only need to figure out the voltage.

Do you program at all?

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JVDE

thank you very much!

Today I allready learned it will take a microcontroller to make the calculations. lol

I have a few visual basic skills, maybee the Basic code is a bit similar to VB??

shotgunefx

If you can figure out VB, you can figure out regular basic.

Well, if you go the "PIC" route, there are a couple ways you can go. Assembly language, which probably isn't what you want, but the PIC Assembler is fairly straight forward, you could use the free version of Hi-TECH C (my choice, but the free version only supports certain part numbers so you want to make sure you buy one that is compatible)

There are a couple versions of basic for PICs with varying degrees of functionality, ranging in price from free to several hundreds of dollars.

If you use a BasicStamp, a project like this should be pretty easy, (RadioShack used to sell a kit in some stores on a dev board with book for (~$65 USD), but the problem (for me) was the relative expense and lack of interrupts multi-tasking. Don't think you'll have this this problem, you basically need to

Read temp1
Read temp2
Sample voltage
update display
repeat

I had a bunch of projects I wanted to do and by going down to the PIC, saved $50 on each one, and some of them couldn't be done at all due to the lack of interrupts,etc, but if it fits your bill and it's the only thing you have planned, it might not be a bad choice for a first project. Fast and easy.

If you go with a PIC (or a different mcu), I'd get one of those Olimex development boards from sparkfun, they are cheap (~1$4), they have the power supply and a (4mhz or 20mhz) external oscillator all set up and even a serial port and the necessary hardware . Having all those bits laid out the first time, removes a bunch of guesswork the first few go-rounds as to "what" exactly is wrong if you have a problem.

If you have a serial port, you could get the PG2C programmer, it's cheap.

PIC 16x series Olimex dev board (~$14)
PIC 16xxxx MCU ($2-$7)
PG2C PIC programmer ($14)
1-wire temp sensors (2 x $2-$3)
a couple resistors ($1)
LCD or VFD Display ($30 - $100)

It's kind of a broad, nuanced topic (and I'm by no means an expert), but it's all kind of going to depend on a mixture of how much you want to spend, how many projects do you have planned, how familiar you are with electronics and programming, and how much you want to learn to make it happen.

You could probably do it all with a stamp in a day or two, so if you just want it done, hard to argue with the overhead of $30 or $40.

Good luck

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JVDE

Oké, thank you very much for this very long post
thank you for making time!

I'll start trying it with the things you say:

PIC 16 series + programmer + all the other hardware
and the high tec-c software

but why do you choose a pic 16 series? I want to follow your thought a bit.

thx once again!

shotgunefx

No problem, it's kind of overwhelming to figure out where to start.

Actually, the reason for the choice was pretty simple, there's a ton of code for the 16F series as they've been around for ages, and that book I mentioned was based on the 16F628 IIRC. I think that's who a lot of people fall in with a particular brand (AVR, etc), I think it's whatever you get familiar with first.

For driving an LCD or reading temp sensors, there is bound to be a ton of code for any MCU you choose, so really the choice is yours.

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Bob4321

Hey
I do Alot of small electronics projects with LCD's. If you are use to basic
and or c code the easiest microcontroller is the fbasic . it's made by proteanlogic. It has a prebuilt library to handle the buss function to talk to the lcd. and schematic of how to hook it up. If you get stuck I can send you some
code examples.

xiaoyou

Hi, for the content you want to display in your car, perhaps LCD and VFD BOTH CAN BE OK. But the better one is VFD Display for car. Because VFD has a quick response abd wide ranging angle, high liability and long service life. Besides, fine Dot-Matrix VFD Display also can supply the best effect for car.

eag182

This would not be a simple undertaking for a beginner, but if you're up to it you might as well take a look at the Arduino dev board too. It's similar to PIC and Basic Stamp.

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xiaoyou

hi, friends, have you used this display in your Car before?

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Can be used in Car's Vedio&Audio, Icons, home appliances, POS terminals, Set Top Box, and so on!

rodweb

This will do all you want to do : www.arduino.cc You should be able to get out of it for about $50.

You program the Arduino in C and download the applciation to its flash memory via USB. The unit will run stand alone, but you can optionally send data back to the PC via the USB serial interface

So you will need to purchase an LM35 or DS1820 for each temperature sensor. which wil cost about $5.00 each and two resistors to create a voltage divider for each voltage sensor for less than a dollar a sensor. So to display it on a 2-4 line display, you should be able to buy one at Sparkfun quoted earlier for about $10-$15 if that.

There are libraries to support the LCD display and the DS1820 on the Arduino Playground. The LM35 is so trivial, it only needs a few lines of code.

The LM35 is an analog chip that puts out 10 mV per degree centrigrade. I think there is also a farenheit compatible equivalent. To display temperatures below 0 deg C, you need to add a negative 5 volt line which is not trivial. I chose the DS1820 because of this and stuck it in the freezer done to about -18 degree C which is roughly 0 deg F. It is a digital chip that you ask nicely to send you it's temperature and it obliges by sending back it's data. This makes the software more complex, but there is a library available for it.

I've tested all of these sensors on the Ardiuino and will be adding temperature and voltages to RR using the established interfaces as well as some relay boards etc shortly.

For the voltage, you have to reduce the voltage to < 5 volts for the Arduino's A/D converter so something like a 4.7k and a 15k one watt resistor will achieve this and give you a top end range of about 20 volts.

There is some good info on the Arduino Forum about this stuff. I have not tried an LCD display but it is also very easy to sort out.

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