Help, electronic experts

[drew1]

Hi,

Trying to program an elecromotive TEC II with a Dell Latitude XPi P133. I get a com error. Called Electromotive on Fri afternoon and got help showing me I had the trottle sensor wired wrong. Was able to correct & read sensor outputs.

Upon trying to program the TEC II (load in timing & fuel changes as sensor outputs change), I get a com error. The TEC II manual says that an old + & - 12V serial port may not work with the TEC II. Measuring from pin 5 to 3 on my 9 pin connector on the Dell, I get -12 V.

Does anybody know how to make a buffer/driver that will translate the + & - 12V to +5V & 0V?

Thanks,
Andrew Love

[Ehab]

There are some standard regulator chips that will do that for you easily ... I'm sorry I can't be more specific since I never made one myself, but +/-5 is very standard in the computer industry. However, I don't see how you didn't blow the card by using +/-12 already!

E

[fprovencal]

HI,

If you want to convert from -12 +12v (RS-232 standard) to 0 +5V (TTL STANDARD) you can use a MAX233 chip.

The max233 is made by MAXIM (www.maxim-ic.com)

You might find more info about the chip and how to connect it.

http://www.compsys1.com/workbench/On_top_of_the_Bench/Max233_Adapter/max233_adapter.html

Also, MAXIM-IC.COM can send "demo" chips if you have a company name. check out their web site!

Hope that help you!

If you need more assistance, e-mail me!
fprovencal at videotron.ca

Francois
Léry, PQ, Canada
Learning and shopping for my first 84-86 red 944!

[drew1]

Thanks Francois,

The Maxim site is real helpful. I suspect that the TEC II has one of their driver recievers in it. It looks like what I have to correct is the old RS232 ports ignoring & not sending in the -3 to +3 Volt range.

drew1

[fprovencal]

HI,

If your unit already have a maxim (or equ) interface (builded-in), the output to the computer should be +12 -12. I never saw a rs232 interface that is using +3 -3V. If you have a RS-232C device, it's should be +12 -12. if you need +5 0V (TTL) format, you must go thru the max233.

To be honest, I don't know anything about the TEC-II device but there is big chance that your TEC-II need +5 0V as input/output data to your computer. On the computer side, it must be +12 -12.

Hope that will help a little bit more!
In the meantime, I'll do search on the tec II device about their data format.

Also, be sure to "twist" the in/out data pins from tec II to computer. More info: http://ewhdbks.mugu.navy.mil/rs-232.htm

Francois

[drew1]

With rain & all, I've been working on shelf building project when not at work. The + & -3 volts on RS232 ports is the ignore part of the sinal so that interference is ignored. I'm thinking that the newer RS232 ports may have a tighter range. I'll lookinto Maxim site more.

Thanks,
drew1