Have issues with your REM + V3.1 or REM II V4.1C Clock Panel freezing up on you or acting erratically? It might be an overheating issue! This guide will show how to upfit your unit with a bigger regulator that can take the heat.
Background:
So first let’s talk about what’s going on. The Arduino brain box needs 5 volts to work. The REM needs to take 12v from the vehicle and bring it down to 5v for the Arduino to be happy which is done with something called a voltage regulator.
The Linear Voltage Regulators used in the REM work by burning off all the extra energy as heat. The higher the voltage in, the more heat is created. That means the device might work great with the engine off at 12v, but could get too toasty at 15v when it’s running.
The regulators have a built in thermal shut off so they will just slowly stop working when they get to about 250ºF. This way instead of catching on fire or burning up in a big mess, they can just simmer and will work again once they cool off.
What happens to the REM at this point is the voltage output will slowly drop from 5v to the point that the Arduino can’t work anymore and then it will do all kinds of crazy things due to this voltage brown-out. It seems that the added Clock draws enough power that the regulators just can’t keep up, so let’s add something that can!
Requirements:
– 5V 1.5A Linear Voltage Regulator # L7805 (link here)
– Soldering
– Razor Blade or Side Cutters
– Slight board Modification
REM + V3.1 Clock Panel Procedure:
On the V3.1 board, power goes from 12v straight to the Arduinos VIN pin for the onboard voltage regulator. We will have to cut this copper trace with a razor to disable the onboard regulator. It’s a bit tricky to get to and there are other traces nearby so you must be careful not to cut the wrong line.
Fair warning, the case can be a little tricky so just be careful. First you will have to bend the case a little in order to pop the REM board out of it’s holding tabs, then flip it over so the buttons are pointing up. Then look under the screen for this trace here:
Grab your trusty Razor Blade and with a slight sawing motion you should be able to cut the copper trace. You don’t have to go very deep, but make sure it is completely cut.
Once you have cut the trace, you should check continuity with a multimeter to make sure it is completely cut. Measure from the pin labeled VIN on the Arduino to the 12V Rail on the board and make sure there is no connection.
Next up is attaching the new Regulator so it can live again!
L7805 Regulator Pinout:
Input will go to 12V, Ground to GND, and Output to 5V.
The nice thing about the REM V3.1 C power rails is that they match the regulator pinout perfectly so we can just plop it in with the heat sink facing the arduino. Make sure to trim the legs before soldering so they aren’t poking anything underneath. As long as there aren’t any solder bridges between the pins then you should be good to go.
Now you can bend it over and you should be ready to test. If the REM powers up when plugged into the vehicle then you did it! Now you should be able to enjoy your REM without fear of heat issues. Stay Cool!
REM II V4.1C Clock Panel Procedure:
On the V4.1C board, 12V goes to an SMD Regulator (VREG) which then supplies the rest of the board with 5V. We will have to disable that regulator’s Input Pin since we can’t get to the trace. Then we can add the big one in and call it a day.
With some small side cutters, clip the Input leg and make sure it is not touching the board anymore. Alternatively, you can also heat up the pin with a soldering iron and bend it up off the board with a very small flathead. Once that pin is disconnected from the board then we can move on.
L7805 Regulator Pinout:
Input will go to 12V, Ground to GND, and Output to 5V.
Due to the power rail breakout order, it is a little tricky to fit the regulator but it is possible. Solder then ground pin first, then move on to the other 2. Remember to clip the legs short so they don’t touch anything under the board.
Recommended that the regulator be bent back like this for USB cable clearance.
Once the regulator is in place and there aren’t any solder bridges, you can test in on vehicle. If it powers up then you should be good to go! Enjoy your REM to its fullest potential now!