Help required in UK with project

Thread Starter

Nick Bacon

Joined Nov 7, 2016
130
Hi all,

I have a project for a complex water level sensor. I have prototyped the board but am having issues with TLC3702CP that keeps blowing. I am looking for someone who could look at the boards and fault find. I am happy to pay for the service within reason.

I live near Southampton, so if there are any electronics guys out there in UK that wold be interested please drop me a line.

board 1.jpg board2.jpg
 

Thread Starter

Nick Bacon

Joined Nov 7, 2016
130
Hi guys, Sorry for the late reply, I have been away for a few days.
The problem is that I have approached this with a complete lack of knowledge. I am trying to get the project working on a shoe string hence trying to do this myself.

A bit of history..... I have a very old schematic and PCB artwork which I have tried to replicate in Design Spark. I thought I had it working after getting some prototype boards made, I needed to make a few modifications to the boards and incorporate some changes. I built up a second set and the TLC3702CP fails straight away.

I did not make a schematic in Design Spark but just did a PCB layout, yes I know this is completely wrong, I struggled with the schematic as I am no electronics engineer, I know the type of equipment and what was needed to modify the original circuit.I have attached photos of the original board, artwork and schematic. I have the Design Spark files I can email but can not post them.

What I am trying to do it replicate just one of the channels (four on the original) I am not using the bottom left section of the circuit that is used for validation. All a bit of a mess I know and it should not be a big job to sort.

IMG_1694.JPG IMG_1696.JPG IMG_1699.JPG IMG_1700.JPG image1.jpg image2.jpg
 

bertus

Joined Apr 5, 2008
20,535
Hello Nick,

There are some restrictions for new members.
One of the restrictions is that you can not start a conversation.
When you reach a postcount of 10, you will have all features available.
When someone else started a conversation with you, you can reply on that.

Bertus
 

ericgibbs

Joined Jan 29, 2010
10,018
hi Nick,
What is the failure mode of the OPA.?
Does it blow up, get red hot, short circuit etc.?
Immediate or delayed failure.?
E
 

Thread Starter

Nick Bacon

Joined Nov 7, 2016
130
hi Nick,
What is the failure mode of the OPA.?
Does it blow up, get red hot, short circuit etc.?
Immediate or delayed failure.?
E
I am beginning to wonder if the failure was caused by the LED display board. I have tried a few things. Trim the input voltage down to 12V from 12.3. I have adjusted a 4.7K resistor down to 1K as the relay was not operating correctly (this has solved the relay issue). I have added an extra ZVN2110A transistor to cope with the addition of a green led to work along side the red one (steam or water). Having done all this and replacing the blown TLC3702CP all seems to be working. The strange thing is that 2 out of the 4 boards I made initially blew the TLC. It was very hot straight away and then failed within seconds.

Since making the mods I have tried everything to try and get it to blow but they are all working still. There are a number of jumpers to select normal relay state (energised or de-energised) and conductivity settings (3 different values).

I will keep on testing and switching the channels and jumpers to see if there is a weakness in the circuit.
 

Thread Starter

Nick Bacon

Joined Nov 7, 2016
130
I have a question relating to relays. The circuit uses a DS2E relay
http://uk.rs-online.com/web/p/non-latching-relays/1278872/
These PCB mount highly sensitive miniature relays all share the same height (9.8 mm) and width (9.9 mm) making mounting on PCB boards easy. They are suitable for use in difficult environments and have high performance polarized magnetic circuits that offer high resistance to shock and vibration.

Monostable range of relays with highly reliable gold clad contacts
200mW nominal operating power
Dual In Line pinning
Sealed construction allows automatic washing
Typical applications include Telecommunications and Measurement equipment, Computers equipment etc

I would like to do a version that uses a larger 8 amp relay
http://uk.rs-online.com/web/p/non-latching-relays/1986905/

Is there any that I would need to do if I want to use this?
 
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