Rs232 help please

Thread Starter

F1 engines

Joined Jun 14, 2022
4
Need help identifying this circuit if there is an off the shelf replacement or if I can have it manufactured.
What I know about it is we use as an interface between a data acquisition and and an ECU that outputs data that is collected on the logger.
the pictured module is powered by 12 volts the has a rx and tx leads.

Any help is much appreciated.
 

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AnalogKid

Joined Aug 1, 2013
10,096
The Sipex part is a very common TTL-to-RS232 interface, made by Maxim, Exar, Analog Devices, Linear Tech, etc. Reverse engineering that part of the circuit should take an hour. The boost capacitor size (4.7 uF) indicates that it either is an older part (newer parts use 0.1 uF caps) or they are using part of the boosted +/-9 V to power something else.

What is the other IC? Please post a better photo of it so we can see the Logo, and type out for us.

1. Does the replacement circuit have to be the same size/shape? If not, what are the size constraints?

2. How many layers is the pc board?

3. There are seven connector pads. Please give us a list of the power and signal connections.

ak
 
Last edited:

panic mode

Joined Oct 10, 2011
2,170
sipex 232 is just an RS232 interface / line driver. cannot read the smaller chip (LM2...?).
how many units you need? with sample like you have it is trivial to reproduce
 

AnalogKid

Joined Aug 1, 2013
10,096
LM293 is an industrial grade dual comparator. IOW, it is rated for a wider operating temperature range than the standard commercial part, the LM393. This is common in automotive applications.

The LM293 means the board is doing something other than basic TTL-to-RS232 conversion. Any idea what that is? Probably not a big deal, but it directly affects the test fixture.

If the board is only two layers, you can reverse engineer a schematic with an ohmmeter or continuity tester.

1. The board looks like it was hand-soldered. Does the replacement board have to be surface mount, or is through-hole assembly acceptable?

2. Pads for hand-soldered wires, or change to actual connectors?

3. Overall size?

4. The board has no mounting holes, so it must be constrained inside an enclosure that matches the notches at the corners. Any information on this?

5. Add the reverse-polarity protection diode to the board design? That's the 1N400x diode on the bottom side.

7. There is no ground wire attached to the board - ?

Where are you located?

ak
 
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Thread Starter

F1 engines

Joined Jun 14, 2022
4
LM293 is an industrial grade dual comparator. IOW, it is rated for a wider operating temperature range than the standard commercial part, the LM393. This is common in automotive applications.

The LM293 means the board is doing something other than basic TTL-to-RS232 conversion. Any idea what that is? Probably not a big deal, but it directly affects the test fixture.

If the board is only two layers, you can reverse engineer a schematic with an ohmmeter or continuity tester.

1. The board looks like it was hand-soldered. Does the replacement board have to be surface mount, or is through-hole assembly acceptable?

2. Pads for hand-soldered wires, or change to actual connectors?

3. Overall size?

4. The board has no mounting holes, so it must be constrained inside an enclosure that matches the notches at the corners. Any information on this?

5. Add the reverse-polarity protection diode to the board design? That's the 1N400x diode on the bottom side.

7. There is no ground wire attached to the board - ?

Where are you located?

ak
Hi Ak,

This is an automotive application so may explain the LM293.
Pretty sure the board is only two layers.
Through hole would be fine, this unit normally has a piece of heat shrink over it, I would like to pot into a plastic housing so size and mounting are pretty open.
Reverse polarity protection would be nice.
There is a ground not 100% on where it goes till I open another one.
Located in Clearwater FL.
Thanks!
 

AnalogKid

Joined Aug 1, 2013
10,096
this unit normally has a piece of heat shrink over it, I would like to pot into a plastic housing so size and mounting are pretty open.
Nothing wrong with a flying splice assembly if you give it a secure mounting. I would add pairs of holes to loop through a small wire tie to secure the wires. The transition from soldered strands to free strands is very susceptible breakage in a high vibration environment.

ak
 

AnalogKid

Joined Aug 1, 2013
10,096
Yes, but they are very far apart. I don't see any useful containment of wires toward the center of the board. I was thinking of one small wire tie per two wires.

ak
 
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