Ramps 1.4 Marlin firmware I decided to add connectors to my extruder stepper, hot end resistor, and thermistor so I can swap out extruders easily. When I wired up the thermistor and thermistor I got them backwards. I briefly exposed the T0 pins on the RAMPs to the heater resistor. No power was going to it obviously because the resistor was hooked up to the T0 pins. The "temp" reported in Pronterface shot up to like 700 degrees. I knew something was not right. Noticed the reversed connections and fixed it. Now, T0 reports 128 degrees. Even if there is nothing attached. The thermistor did not get damaged because I tested in on the T1 pins. Could exposure of the heater resistor to the T0 pins have damaged the RAMPS? I have reset the Arduino. Reflashed. Completely unplugged the RAMPS and let it rest. Thoughts? I can move the extruder temp to pin T2 that is not in use. I am very curious what is wrong with T0 however. https://reprap.org/forum/read.php?219,308070,308070#msg-308070 Mon, 16 Mar 2026 11:27:57 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?219,308070,308734#msg-308734 https://reprap.org/forum/read.php?219,308070,308734#msg-308734 jamesmoe RAMPS Electronics Sun, 09 Feb 2014 19:32:10 -0500 https://reprap.org/forum/read.php?219,308070,308392#msg-308392 https://reprap.org/forum/read.php?219,308070,308392#msg-308392 Cefiar RAMPS Electronics Sun, 09 Feb 2014 02:07:22 -0500 https://reprap.org/forum/read.php?219,308070,308357#msg-308357 https://reprap.org/forum/read.php?219,308070,308357#msg-308357
I have a plan B .. but lesson learned.

Thanks.]]> jamesmoe RAMPS Electronics Sat, 08 Feb 2014 22:47:51 -0500 https://reprap.org/forum/read.php?219,308070,308343#msg-308343 https://reprap.org/forum/read.php?219,308070,308343#msg-308343 cat.farmer RAMPS Electronics Sat, 08 Feb 2014 21:28:12 -0500 https://reprap.org/forum/read.php?219,308070,308269#msg-308269 https://reprap.org/forum/read.php?219,308070,308269#msg-308269
This is sort of a known problem with RAMPS and most other electronics, that the thermistor inputs are usually not protected against voltages >5V. Some of the newer boards out there have this protection, but RAMPS is now a pretty old design.

Note: The way the hot end output works, there is ALWAYS 12V on the hot end, so even if you didn't turn on the hot end, it will definitely have exposed the thermistor to >5V.]]> Cefiar RAMPS Electronics Sat, 08 Feb 2014 17:44:37 -0500 https://reprap.org/forum/read.php?219,308070,308086#msg-308086 https://reprap.org/forum/read.php?219,308070,308086#msg-308086 With it disconnected what does your ramps report?]]> cat.farmer RAMPS Electronics Sat, 08 Feb 2014 09:25:36 -0500 https://reprap.org/forum/read.php?219,308070,308070#msg-308070 https://reprap.org/forum/read.php?219,308070,308070#msg-308070 Marlin firmware

I decided to add connectors to my extruder stepper, hot end resistor, and thermistor so I can swap out extruders easily.

When I wired up the thermistor and thermistor I got them backwards. I briefly exposed the T0 pins on the RAMPs to the heater resistor. No power was going to it obviously because the resistor was hooked up to the T0 pins.

The "temp" reported in Pronterface shot up to like 700 degrees. I knew something was not right. Noticed the reversed connections and fixed it.

Now, T0 reports 128 degrees. Even if there is nothing attached. The thermistor did not get damaged because I tested in on the T1 pins.

Could exposure of the heater resistor to the T0 pins have damaged the RAMPS?

I have reset the Arduino. Reflashed. Completely unplugged the RAMPS and let it rest.

Thoughts? I can move the extruder temp to pin T2 that is not in use. I am very curious what is wrong with T0 however.]]> jamesmoe RAMPS Electronics Sat, 08 Feb 2014 08:51:05 -0500