Comments on: TTL to RS232 adaptor Explained

By: Daniel

Daniel — Wed, 21 May 2008 18:02:46 +0000

If you need a pre built RS232 to TTL device or can't get the goods shown, then an alternative is available. See Tronisoft for more info. They do a few different versions of RS232 to TTL devices including one where you can power it via a 9V Battery! The only problem is that it does not show how much it costs for worldwide delivery but if your in the UK or Europe then your fine! I've copied the links from their website for you guys if it helps! The whole selection RS232 to TTL level converters Kit Version! RS232 to TTL (5V Signal) Converter Kit The one I was talking about! powered via a battery. RS232 to TTL Level Converter (5V Signal) with PSU Dan

By: Jeff

Jeff — Tue, 22 Apr 2008 05:12:03 +0000

I dont know how old this thread is but i am sure glad you put this together. I would just like to say that the circuit did not work as it is shown. After about 30 hours building and rebuilding i found what works for me. I looked over the max232a chip schematic and wounderd why they tied 4,6 and 8 togather low and behold, pin 2 did not need to be connected at all , rather tie pin 4 6 and 8 up to a single lead and insert on the collector of the pnp transistor. this fix on my p1110 dell 21 ” monitor i got out of the trash cost me zipp nothing. you can get the parts out of an old radio. again thank you very much for taking the time to build this site.

By: Manish Meshram

Manish Meshram — Wed, 16 Apr 2008 02:08:25 +0000

it is very nice , i generally used serial communication in my design , it is too difficult for pcb routing ,and it is not cost effective with 232 chip even it required 3-4 capacitor .

thank you , for the design , i hope i will save silicon chips through this design from my next design !

By: t1000x

t1000x — Sat, 12 Apr 2008 05:28:18 +0000

i saw a project from a website;www.weavefuture.com. I studied all the details, pictures, informations and already downloaded all the softwares needed from the site. I started to gather the materials to test the project, but its only a local parts I got. A PC, a coin selector HI-06cs, a timer circuit using ATMEL 89C51 which is really different from WEAVE FUTURE cos it doesnt have an RS232 connector terminal. I just assumed that pin 10 (RXD) and pin 11(TXD) of 89C51 were directly connected to pin2 and pin3 of RS232 terminal. So i got an old SERIAL MOUSE (RS232), cut its wire, and configure the color wirings according to its pin # connection. then i connect it to pin 10 and 11 of 89C51 in accordance to pin terminal of RS232. I followed the instruction in WEAVEFUTURE on how to install the software, but when i test my project, i was upset The software was not responding, but my timer counts. I assumed that my idea in this project was missing something like additional circuits or programs.
And now, im asking all of you goodhearted people to share me some info or tips that would might be helpful for me in accomplishing this project.

By: Tim_in_ATX

Tim_in_ATX — Thu, 13 Mar 2008 08:23:14 +0000

Thanks, for the circuit it was just what this noob needed.
I think either the 3904 is backwards or I am.
I first built this circuit with 4401 and 4403 transistors and it didnt work. Then I added a negative supply to the circuit and reversed the transistor and it works. I buit my neg supply with a 555 cap charging circuit and a zener diode. After all that fun it works perfect, although I still dont understand why the 4401 and 4403 didnt work. They did function @ slow speed when tested with a Vmeter and jumpers, but not on a rs232. The 4401 and 4403 should be operating saturated and the data sheets say they are good to 200 MHz.
Thanks again for the circuit. : )

By: dfowler

dfowler — Fri, 29 Feb 2008 07:54:32 +0000

Peter,

I dont present a specifc converter here. The max limit would be dependent on the load and the length and type of cable used. I expect that any of these circuits would work fine for cases where the baud rate is not very high, say 115KBS.

By: Peter

Peter — Wed, 27 Feb 2008 14:50:09 +0000

What is the maximum baoud rate that you can achieve using your converter?

By: Phil

Phil — Mon, 11 Feb 2008 04:37:27 +0000

Nice article. I have found this board – a TTL to RS232 module with buit in PSU available in UK
from http://www.tronisoft.com/4201.php

By: WD5GNR

WD5GNR — Sun, 03 Feb 2008 20:20:18 +0000

Also have a look at http://www.awce.com/rs1.htm if you want a ready to go solution with handshaking lines.

By: dfowler

dfowler — Thu, 23 Aug 2007 04:18:45 +0000

Charles,

The TX pin on the TTL side is an output from the device which needs to be converted. The output should be tied to the base as shown.

I think the problem stems from the use of TX and RX. When a pin is labeled “TX” is that where the transmiter ties to drive the output signal or is that the TX signal from the external device that should be tied to the receiving input?

Does anyone know of a real standard that solves this problem. I have put arrows or included “Out” and “In” in the names to help make this clearer, IE “TX_Out” but even that could be confused.

I always name the signal from the described devices standpoint. TX would be the TX output of the device drawn in the schematic. But it seems that in this case I failed to follow my own convention.