Almost total ignorance

[DALEK]

Hello world,

I am an electronic engineer but when I was in university there were only six computers on the entire campus. It wasn't a bad university it was just a long time ago.

Now I must make a LCD display thermometer at low cost, high accuracy and with a very long battery life. I took the liberty of peeking inside a competitors product and they use a PIC16f628A.

I cannot overestimate my ignorance of these modern devices.

Can someone tell me what development kit and software I need to buy?

Thank You.

[Al_The_Man]

If you visit the PicMicro site, they have all the Free development software, compilers,debuggers etc you need, including App notes.
For a programming module, there are many designs out there or a cheap one by Kitsrus.com
Also there is a text book by Mike Predko that has a printed .CCT card comes with it to build one.
For online tutorials see the Nigel Goodwin tutorial site if you want to get started with interfacing etc.
http://www.winpicprog.co.uk/
Al.

[amplexus]

1 How high of accuracy over what range? if the range is wide you probably need platinum rtd. Thermistors are not very linear but the nonlinearities can be compensated for.
2 build everything possible usinf cmos for low power
3 steal the plans, there are tons of free schematics out there.
4 use a low duty cycle sampling to save power
5 consider a solar cell battery charger
6 a pic may be overkill
Amplexus

[Eurisko]

... a pic may be overkill
Amplexus

A PIC is overkill, but it's time to jump in and meet the competition head-on

The PICs are fast, reliable, and energy efficient. They offer sleep modes to save energy, and internal oscillators to save valuable board space (and money).
In addition, the PICS can be reprogrammed in circuit, which is a nice feature.

I'm strictly a PIC hobbyist, would love to have more time investigating what these amazing chips can do.

BTW, I use an Olimex PIC programmer. I highly recommend it.

There are a ton of development boards for PICs. Make sure that your programmer is MPLAB * compatible; it really makes developing code easier.

* PIC programming software suite, free from Microchip



Good luck, and have fun.

[DALEK]

Thanks for replies guys.
I have looked at the Pic Microchip website but it is like looking at a bucket of frogs.
I have designed dozens of circuits using RTD's Thermocouples etc, so I dont have a problem with the linear end of the circuit. I need to make a thermometer which is accurate to about 0.1% and a permanent LCD display which updates about every 10 seconds. I need a battery life of some years with two AA batteries. I think this is a mathematical impossibility with the type of circuits I am used to. Also it would be an advantage to make the device programmable for different sensors, maybe max/min also.
If I use some ultra low power linear cicuitry, a 16f628A and a AYO438 display driver is this possible?
Are you saying that if I buy a development board and a MPLAB compatible programmer I can download the software I need free from the Microchip website. I have plenty of time to play around at the the moment as business is so bad.

[Al_The_Man]

The MPLAB is free to download off the site.
This gives you all the development tools except the programmer itself, which is not that much to buy or build.
I also suggest you download the two manuals, IDE Users guide & the MPASM assembler guide.
Also the Data Sheet for the Chip you are using.
I found Nigel's site very helpful when getting started. He shows the analogue input technique together with the common HD44780 or variation of the LCD 2 line display is often used with these I.C.s which also have serial out for the data.
I am not familiar with the AYO438, who makes it?
BTW FuturLec sell the prototype boards shown on Nigels site.
Al.

[mckban]

For a programmer I would highly recommend the Pickit2 or Pickit3 (which I haven't used yet) from Microchip. $35 last I looked and it supports about all of their chips. If you want to program in assembly then MPLAB is free, but for a good low cost C compiler look at www.sourceboost.com The price is better than any other I've found, and generates some very compact code. For low power consumption I think Microchip has some newer low power chips, and I believe most of them have sleep and other low power modes that will help.

[amplexus]

Do you need a bridge and a platinum rtd or will a thermistor do? what is your temp range?
I think you have a better chance with discrete cmos chips than with a pic, (I love pics but for this they may not be the best choice. )
Seriously cosider a photovoltaic and lithium rechargable batteries.
avoid backlit displays
choose as small as possible lcd
Less frequent updates if possible
Amplexus Ender

[Al_The_Man]

Among my decision for opting for a Pic would the greatly reduced real estate over discrete IC's also cost is not an issue when Pic's run from $1 to $5.
Al.

[amplexus]

Pics are cheap and easy, if not for the power constraints they would be my first choice as well but they are not ultra low power.

Amplexus

[Joe S.]

Hello DALEK,
Programmer / Development PICKit2 and the low pin count demo board, comes with an 16F690 PIC for about $50 or so US. For software, MPLabs PIC Basic Pro IMHO @ $249 full version with manual.http://www.picbasic.co.uk/forum/ this link will direct you to a great forum, dedicated to PICs. Throw in a couple of low cost breadboards, some LEDs and jumpers and you are on you way for less than $400 US, you could do it a bit cheaper using a JDM and ICPROG to program, but the PICKit with demo board reprograms each time you recompile with no extra button pushing or removing of the chip. Note: PBP only works for 8 bit PICs all 12Fs, 16Fs,18F chips, noDSPic or beyond, still lots of things can be done with 8 bit chips, most certainly the project you mentioned. With PBP you can use it's assembler or MPASM and you can incorporate assembly routines into your basic program. This is NOT an interpreted basic, it compiles standard INTEL HEX just like C, or assembly does. It is available from Crownhill in the UK, BTW Microchip was offering a reduced price on PICKit2 in the EU, I on the other hand paid Full Price.
Microcontrollers are like automobiles, the faster you make them go the more they consume, if you select a chip with low power OSC and run it slow, sleep between check cycles, you can drive down their power requirements dramatically.

[DALEK]

Thanks for all your replies guys,
I definately need a RTD for this project, for both the range and accuracy, about 500* Celsius.
The display driver chip I mentioned is a AY0438 ( my typo) which is made by the same company as the Pic. It just takes serial input and outputs to digits.
I can see everyone is enthusiastic about these devices so I have managed to get hold of a Picdem 4 development kit. I will play with it until I get a headache and let you know how I get on.