Alternatives of MAX232 in low budget projects
-->Sometimes when you work on low budget projects of don’t want to go shopping for max232 or similar IC you can save your time and money by using other TTL to RS232 converter. We usually used to use MAX232 chip like this:
Max232 IC is a specialized circuit which makes standard voltages as required by RS232 standards. This IC provides best noise rejection and very reliable against discharges and short circuits. If your project is more advanced and has to reliable you must use specialized RS232 to TTL converter IC’s. As I said Specialized are more expensive than other solutions.
One of such solution is Transistor based interface:
Transistors can be any general purpose transistors. This circuit is very easy and works without problems. It is cheapest solution as it require couple of transistors and four resistors. Two transistors does a trick to get a negative voltage as required by some PCs. When the PC does not transmit data, its TX pin is stuck to a negative voltage. The negative voltage is picked up from the TX pin and brought back – through resistor R3 – to the PC’s RD pin.
RS232 alternatively can be interfaced using Logic gates. This is handy when your application is using logic elements and there are couple gates left on some IC. As almost every PC can vork with positive-only signals logic gates can provide necessary inversions. For instance using CD4066B CMOS IC:
And of course NAND and NOR circuits:
And don’t forget to Power the logic IC’s with 5V.
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August 25th, 2007 at 12:39 am
[...] circuits of MAX232 – [Link] Filed in [...]
August 28th, 2007 at 9:47 am
uCHobby has an article describing how the two transistor RS232 converter works. You might find it interesting to reference.
http://www.uchobby.com/index.php/2007/06/11/ttl-to-rs232-adaptor-explained/
February 12th, 2008 at 11:51 am
Hi,
Good to know about this article. However if you need the full 5-pin interface and are working with long RS232 cables at high speed it may still be useful to use a MAX232 IC.
You can get the following quite cheap:
http://www.tronisoft.com/4201.php
The thing like is the PSU is built in so you can power the circuit and you Microchip PIC projects in one go. Great for breadboarding!
Dan
November 18th, 2008 at 4:56 am
[...] Diterjemahkan dari artikel asli: “Alternatives of MAX232 in low budget projects” [...]
March 29th, 2009 at 7:17 am
Great all-in-one-place article!
I was about to use a Max232 to “translate” old vintage computer current-loop to RS-232. This is called a 20ma current loop digital interface. NOT to be confused with more contemporary 4-20ma current loop analog interface. (Did I get that right?).
Is there a simple sans-Max232 circuit for this (adapting 20ma current loop to RS-232)?
Scott
April 19th, 2009 at 12:29 pm
The MAX232 schematic is wrong (at least it didn’t work for me)!!!
I used this schematic
http://www.captain.at/electronic-atmega-mmc.php
April 19th, 2009 at 1:53 pm
Max232 works for me. Could be other factors that cause failure.
June 28th, 2009 at 3:00 am
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December 8th, 2009 at 7:11 pm
[...] WRT54G) with a PC. But what if you want a simple (and, more importantly, cheaper) alternative. This article from Scienceprog.com should scratch your itch. Share this [...]
December 22nd, 2009 at 1:35 pm
Hi, I’m building an unlocker cable for my cellphone but I don’t have access to a MAX232 which is required. Can I use any of the above alternatives instead ??
Thanks.
December 23rd, 2009 at 12:49 pm
Sure you can try. Most computer will work fine with any converter. But some may be sensitive to different RS232 signal level. Just give a try.
January 16th, 2010 at 6:10 pm
Hi
What is different between MAX232N and MAX232 ?
Thanks
February 3rd, 2010 at 11:29 am
Thanx =)
February 18th, 2010 at 2:50 am
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