Improving the T-962 Reflow Oven

When I got my first reflow oven, the T-962Infrared-IC-Heater-Reflow-Oven-T-962--340x270, I was a bit disappointed with the built-in firmware.  After I’ve made the several must do improvement hacks shown here, here and here. I’m still stuck with the badly written firmware and keep scorching many of my boards using the in-built profiles. There is a replacement controller available but it cost almost as much as the oven itself! Besides, the built-in controller has an ARM LPC2134 processor on board, it seems a waste not to make the most out of this 32-bit processor.

I was delighted to found that Mr. Werner Johansson of Unified Engineering has managed to improve the firmware of the T-962 Reflow Oven. His firmware has much enhancement over the original and by adding new thermocouple amplifiers, you can get more consistence results. Mr. Johansson makes use of the MAX31850 thermocouple amplifier from Maxim, which is a One-Wire device. His choice of this amplifier is due to the free pins available on the original controller. However, the MAX31850 comes in TDFN package. For those who has little confident to hand solder a TDFN package, I’ve a less elegant solution here. It does require extra chips and small modifications, but all the chips are available in either SO-8 or TSSOP package which even I can hand solder without any problem.

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10 thoughts on “Improving the T-962 Reflow Oven

  1. Hi 🙂
    I want to get a decent reflow oven, and have seen the new firmware on github, but i’m not really sure about the steps into doing it all.. i’m also not sure if i can keep the oven as it is, and only change the firmware, or if i need to add new Thermo couples and hardware for that to use the new firmware.. ?

    Could you maybe lead me in the right direction.. ? doesen’t seem like anyone have done a youtube guide on this firmware change yet – which would be really helpfull for a lot of people i think.. 🙂

    Best regards from Denmark

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    1. Werner and his team have made a lot of improvements to the firmware not just for new add-on hardware, but also fully compatible with the original design. The minimum suggested add-on is the DS18B20 digital sensor for cold-junction temperature compensation. If you want more accuracy, you can upgrade to the digital thermocouple amplifiers suggested here for the SPI version or an I2C version as described at Werner’s github site.

      To flash the new firmware, you’ll need a FTDI USB to 3.3V serial adapter like this one or similar from ebay. Make sure it’s for 3.3V devices or selectable to 3.3V, otherwise you’ll risk frying your controller board!

      To get the controller board into firmware upgrade mode the first time, you’ll need to follow Werner’s instructions here. Once you’ve got the new firmware in place, subsequence upgrades will only require you holding the F1 key while powering on the oven. It’s really just that simple.

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      1. Hi yvrpwl,
        Thanks for your reply..! 🙂
        I have two questions that i have a hard time finding an answer for..

        First..
        Is there any difference on how the T962 performs vs. the T962A – i know they are different sizes and have different wattage (I believe because of more elements in the “A” version?)
        Is one performing better than the other with the new firmware, since it sounds that they are equally bad with the default firmware.. 🙂

        and last..
        The last part you wrote about holding the F1 key, is that something you only have to do once after uploading the new firmware, or is that every time you turn on the oven..?

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      2. Hi Rone,

        Yes, the T-962A is the bigger brother of the T-962 with 1500W heaters. I have the smaller T-962 model and I believe Werner also has the same model too. However, both models use the same controller board and the new firmware should work on both. Depending on what you want to do, the larger model allows you to reflow larger boards. Because of the higher wattage heaters, the T-962A uses external SSR to control the heaters instead of using the on-board SSR.

        If you’ve read Werner’s instruction on how to flash the firmware, you’ll notice that you need to do put the CPU into bootload mode by holding the reset pin (pin1) and bootload pin (pin2) to ground, (pin 1 is next to R27) then you let go of the reset pin while the bootload pin is still grounded. This will put the CPU on the controller in firmware update mode. With a 3.3V FTDI serial cable attached to Rx, Tx and Gnd pins on the ISP (pin 3, 4, 5), you can use NXP’s flash utility to flash the new firmware.

        Once the new firmware is flashed, you no longer need to do the “hold reset/bootload pin to ground” stunt for subsequence firmware updates, all future firmware updates can be done by holding the F1 key during power up of the oven and the firmware will drop you into update mode automatically. You still need the 3.3V FTDI serial cable attached to the ISP port in order to flash the new firmware with the NXP utility. For normal operations, there is no need to press any keys during power up.

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      3. Hi yvrpwl,

        On behalf of your great feedback, i have just ordered the smaller of them – T962… 🙂
        Could i even use an Arduino to act as the programmer in ISP mode? Otherwise the Price of that FTDI cable is Pennies…
        I see that I misunderstood the thing about the F1 key in your previous explenation 🙂 Get it now..! pretty neat that the F1 key during startup can put it into update mode for future updates to be added easily..!

        Thank you for taking your time to explain..!

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      4. Hi Rone,

        The simple FTDI cable is sufficient, just make sure you’re using a 3.3V cable. Some cable can switch between 3.3V & 5V, so make sure you check the voltages on all the pins of the cable before plugging it into the ISP socket, otherwise, you’ll end up with a dead controller board. YOU HAVE BEEN WARNED. 😉

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  2. Hi yvrpwl,

    Thanks for all your feedback – just got the oven and took it apart and removed all the paiters tape as a start 🙂

    Also recieved my FTDI – UART 3.3v cable, and i have two question before i start tinkering.. 🙂

    1. does the T962 need to be powered by mains before i can program the controller, or should i supply power to the controller from the FTDI cable?

    2. I have the version with the terminal block with TC directly mounted (no copper wires).. I found a source for the DS18B20, but I’m a bit in doubt about the small smd component that’s added on the control board.. Is it just a resistor with a random value, or specific value? And does pin 1 and 3 of the DS18B20 just go to the ground plane on the board as it looks to on the image on the github page ?

    Hope to hear back from you soon – looking forward to getting my new oven up and running.. 🙂

    Thanks in advance..!! 🙂

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    1. Hi Rone,

      You should always switch on the main power to the controller before plugging in the FTDI cable. You should never power the controller from the FTDI cable, it just won’t able to supply the current needed. Some of these cables supply 5V to its power pin, (usually in red), so be careful! Measure the voltage output of those pins on the cable just to make sure, NEVER feed 5V to the ISP socket. You’ll only need 3 pins from the cable, Tx, Rx and GND plus two more cables connected to ground for the “hold reset/bootload pin to ground” stunt. 😉

      The TCs are normally connected to the controller via the terminal blocks. The DS18B20 is configured to use parasite power mode, so both pin 1 and 3 are grounded. There should be a 4K7 resistor connected to pin 2 and pull up to 3V3. (Hence the SMD resistor) This will supply power to the device via pin 2, which carries both power and data. Make sure pin 2 is soldered to the correct pad (as shown in the picture) on the controller board as the firmware reads the DS18B20 data from the pin that is connected to this pad.

      I hope this will clarify the issues you’ve encountered, once you’re done, may be you can take some pictures and share with us.

      Happy tinkering.. 😉

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  3. Hi yvrpwl,

    Thanks a alot..! 🙂 Now running firmware v0.5.1 !! 🙂
    Added a small fan on the SSR headsink – keeps the overall temp in the top of the oven Down to a minimum (before it got kinda hot due to bad flow).. Also planning to change the noisy ventilation fan next to the control panel (to one with more flow and less noise)..

    Just ordered the DS18B20 in hope that it will be a bit easier to “trim” the offset.. Otherwise the unit Works well and soon has it’s first real test.. 🙂

    The min fan speed in the settings – is there a “golden setting” here, or is it just trying around? Set mine to 10 right now, but not sure i get enough circulation..

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    1. Hi Rone,

      The firmware version you’re using already has support for system fan control. The system fan turns on only when the compartment above the oven is over 40°C. Once the temperature falls below the threshold, the system fan turns off. Peace and quiet! The temperature measurement is done via the DS18B20 or MAX31855 or MAX31850 if installed. All you need is a FET connect to the AD0 pin as described in Werner’s Wiki under “System fan control”. You can also refer to my schematic shown in part 2. Just substitute the SMD FET BSS138 with a TO92 version, like 2N7000, as the fan doesn’t draw too much current.

      The minimum fan settings is a bit temperamental, depending on whether it’s your first run, where your oven is located and what season you’re in, you’ll need to do a few test runs before a real production run. During the winter months, you don’t want to run your fan too fast, otherwise the fan will draw too much cold air into the compartment, while the poor heaters are trying hard to keep up with the profile. In the hot summer months, bringing the temperature up to the profile may not be much of a problem. The LCD screen will show you how well the oven is following the profile. It’s a lot more accurate than the original firmware, so you can use it to help you to measure your minimum speed settings.

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