12/14/2023 0 Comments Reflow smdNew to soldering? No problem, check out basic soldering tutorial and surface mount soldering guides. This caused the actual temperature to be considerably higher than the measured value.As devices get smaller and smaller, surface mount devices (SMD) are becoming more popular. As an alternative to traditional, larger through hole components, SMD components save space on PCBs. One glance at the tiny size of the components can be intimidating at first but the reflow soldering method makes it simple. Reflow soldering is not only quick but also inexpensive, especially for batch jobs. I initially used the threaded M6 thermocouple (shown below) that came with the Ma圆675 module but I found the temperature reading would lag behind the actual temperature due to the thermal mass of the bolt. The MAX6675 digitizes the temperature from a type-K thermocouple and outputs the data over a 3 wire SPI bus to the Nano. Fixed resistors are used to set the LCD contrast voltage but a potentiometer could also be used. The 1602 LCD is configured in 4 bit mode to reduce the Nano’s I/O count. The top and bottom oven heating elements are controlled by the Nano with separate SSRs. A PC is needed to reprogram the Nano or to capture the temperature data for graphing. A USB power supply is also plugged into the strip to provide 5 volts DC for the Arduino Nano, LCD, and temperature sensor if the cable is not plugged into a PC. The oven AC plug goes to a plug strip with an on/off switch. Refer to the schematic at the bottom of this guide to see how the oven was wired. Perhaps I’ll add some of these items in the future if I want to use lead-free solder. ![]() The oven is performing well enough for tin-lead solder. I chose not to spend any more money to add a 3rd heating element, Reflect-A-Gold tape, door gaskets, or a servo motor. When looking for a toaster oven to convert, it's best to keep it small and simple. This is the Hamilton Beach model 311-34 toaster oven I bought for $10 at my local Goodwill store. The minimal features of my oven bring the cost down to under $100. ![]() 5 volts DC is provided via a USB cable from a PC or power supply. The oven is powered from a plug strip with a switch. The software tells me when to manually open the door during cool-down so there is no servo motor. If a different solder profile is needed, new Arduino code must be downloaded. There is no power switch, touchscreen, or input buttons of any kind. An inexpensive Arduino Nano has just enough I/O’s to control two solid state relays (SSRs), read the temperature, and talk to a 16x2 liquid crystal display (LCD). ![]() With the lower melting temperature of leaded solder, I don't need to add a 3rd heating element. ![]() My requirements are not as challenging as Whizoo’s because I only solder one small board at a time and I use standard tin-lead solder. Besides, it’s a lot more fun to figure out my own design and learn along the way. I used many of the Whizoo methods for sealing and insulating the oven but I’m on a tight budget and can’t afford their kit. There are tons of examples on the internet but I believe the best one is from Whizzo. I’m getting too old to solder surface mount devices by hand so I decided to convert a toaster oven into a reflow oven.
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