This PCB provides a quick solution to implement many of the suggested improvements for the T962 & T962A re-flow ovens. Whilst this might look a little pricey the cost of components on this PCB are in excess of 30 pounds and the remaining profit goes towards my time for soldering and testing the board as these are only being produced on a small scale. Plus this will save you hours of messing around buying components, making breakout PCB's and hacking stuff onto the existing controller board. I've also invested a considerable amount of my time and money to bring this solution to you.
Firstly, I would like to extend my thanks to the people behind the Unified Engineering rewrite of the controller firmware for the T962 / T962A PCB re-flow ovens. The original firmware on these ovens was very poorly designed. This rewrite turns the oven from just about being serviceable into an excellent product for the price. The T962 is the smaller re-flow oven. Personally I have gone with the T962A the slightly larger oven and my experiences are based around this oven, however the Unified Engineering firmware applies to both of these oven and many of the oven hardware issues have the same fixes.
There are lots of things not to like about the stock T962 / T962A reflow ovens but the one plus that makes it so popular for the hobbyist and small shop is the price. At around 250 pounds you get a reasonable amount of hardware in a sensible and functional configuration.
However there are a few things that need to be address before you plug it in for it's inaugural test:-
- Check the earth connection. They all have a three pin connector power connector, the standard computer / kettle lead. Internal earthing is done by bonding to the metal case using a screw on the power connector to hold the cable however no effort has been made to remove the insulating paint first. This can be tested using a multi meter to measure the resistance between the ground pin and the chassis. If it's anything above a few ohms I would strongly recommend removing the connection and using some sandpaper or sharp knife remove the paint around the connection so a good contact can be made.
- Replace the masking tape. I have no idea what possessed the manufacturer to use masking tape to hold the insulation in place. This stuff emits the most god awful smell when it is heated up. A smell that feels like it will induce cancer within minutes and to add insult to injury it malingers for days on end. The good news is that it is super easy to fix. Simply remove the tape, preferably before you use the oven as it can be a real pain once it has been heated, and replace it with some high temperature Kapton tape. This completely resolves the toxic fumes issue and the oven becomes a pleasure to work with.
AFTER these two modifications your oven is now safe to turn on.
I would suggest doing this and having a play with the original firmware. Possibly even go as far as to re-flow a few boards and get a feel of how the oven works in it's current state. It will in all likelihood work but the interface is slow and if you work lead free like I do you can have issues with burning of the PCB's when attempting to re-flow them.
The T962 / T962A Controller Upgrade provides the following enhancements to the re-flow oven.
- It enables you to easily flash (reprogram) the controller board with the Unified Engineering firmware, without having to mess about with shorting the reset and n_isp connections or worrying about ttl level conversions for uploading data if you are using a 5v uart device.
- The controller allows 1 Hz monitoring of re-flow profiles. This is done by connecting a PC to the USB port on the Controller Upgrade board and accessing the data using terminal software such as putty to receive the one second updates.
- The addition of four cold junction compensated thermocouples. The two existing thermocouples have not been connected properly in my opinion. They are reliant on the ADC conversion of the controller mCU which doesn't give enough resolution to obtain accurate temperature changes and, far worse, there is no cold junction compensation. Instead the cold junction is assumed to be 25 C rather than being actively monitored. Given that the cold junction is on the controller PCB, which sits above the oven, the cold junction temperature will fluctuate by many degrees C during re-flowing giving rise to considerable inaccuracies. The small fan on the side tries to keep the temperature above the oven constant but really doesn't do an effective job, on top of that it also makes an annoying sound during the whole time the oven is powered on.
Moving the two existing thermocouples from the controller board to the upgrade board allows the firmware to actively monitor the cold junction temperature, ie the temperature of the chamber above the oven, and the small side fan is then only turned on when the temperature of this chamber rises above 60 C which rarely happens unless you are using the oven to continuously re-flow boards. The MAX31850 provides 14-Bit, 0.25°C resolution with integrated cold junction compensation providing far better accuracy than the original system. Additionally there are a further two thermocouple connections which if connected can be attached to the surface of PCB's in the oven to get an actual reading of the surface temperature of the PCB at that point. This is great for sensitive devices that need to have a very accurate re-flow profile.
- A motor controller for adding an optional circulation fan to the inside of the oven to improve the heat distribution over the entire re-flow tray. This requires significantly more work than the above modifications requiring the making of a fan and motor mount and sourcing a motor but once in place can improve the balance of temperature across the whole of the re-flow area rather than having hot and cold spots. I'm not sure if this is really needed but I will do some further investigation to see if this improvement is worth the the effort. I decided to put this on here to facilitate those that had a wish to attempt this modification.
- Finally you can control the oven over the USB connection to allow almost infinite profiles to be used. This would be an ideal job for something like a raspberry pi with a web interface to keep track of historical profiles and the ability to control the current profile. Even to upload new firmware releases.
Connecting the T962 / T962A Controller Upgrade board to the existing controller board is as simple as pushing it onto a 5 pin header and doing a small amount of soldering to contacts on the controller board to provide connectivity to some of GPIO pins on the controller board and to access the power supplies to drive the board at 3.3v and to provide 12v power for the motor controller.
If you want to operate the oven without having a powered USB connection attached to the oven then there are two options; either bridge the R7 resistor pads with the supplied 0R 0603 resistor or a blob of solder or a short bit of wire. The second option is to cut the trace on the bottom of the board which goes to the RST pin as this is only needed to program the oven for the first time with the new firmware. Once you have reprogrammed the oven you can enter programming mode by holding down the F1 key during power up.
T962 / T962A Controller Upgrade
- Product Code: TIP-T962-001
- Availability: Out Of Stock
Tags: T962 T962A