Skip to main content

Portable OBDII Memory Saver

Tired of losing ECU and radio memory when I replace the car battery myself, I followed the instructions in this video and made my own ODBII memory saver.


The gadget is extremely simple to make. I ordered the ODBII plug and A23 battery holder. The diode could be any small signal diode that you have around the toolbox (I am using 1N4148).


Then simply solder:
  • Battery holder GND => pins 4, 5 on OBDII
  • Battery holder VCC => diode (+)
  • Diode (-) => pin 16 on OBDII

That's it. Stuff the battery holder into the empty part of the shell and reassemble. I didn't even bother to screw the shell together.


You can check by inserting a battery and measuring the voltage across pin 4/5 and pin 16. It should be around 12.6V (for a fresh A23 battery) - 0.4V ~= 12.2V. Anything above 11V should work well enough to keep the ECU and radio memory while inserted.

To use, first insert the memory saver into the OBDII port in the car. Then remove the car battery and perform the battery replacement. Finally remove the memory saver.


Comments

Popular posts from this blog

Update: Line adapter for Ozito Blade Trimmer

Update (Dec 2021): If you access to a 3D printer, I would now recommend this solution , which makes it super easy to replace the trimmer line. I have been using it for a few months now with zero issue.

3D Printer Filament Joiner

I have been looking at various ways of joining 3D printing filaments. One method involves running one end of a filament through a short PTFE tubing, melting it with a lighter or candle, retracting it back into the tubing and immediately plunging the filament to be fused into the tubing: One problem with this method is that you can't really control the temperature at which you melt the filament, so you frequently end up with a brittle joint that breaks upon the slightest bend. Aliexpress even sells a contraption that works along the same line. As it uses a lighter or candle as well, it suffers from the same weakness. I am not even sure why you need a special contraption when a short PTFE tubing will work just as well. Another method involves using shrink tubing/aluminium foil, and a heat gun: But a heat gun is rather expensive, so I wanted to explore other alternatives. The candle + PTFE tubing method actually works quite well when you happen to melt it at the rig

Attiny85 timer programming using Timer1

This Arduino sketch uses Timer1 to drive the LED blinker: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 /* * Program ATTiny85 to blink LED connected to PB1 at 1s interval. * Assumes ATTiny85 is running at 1MHz internal clock speed. */ #include <avr/io.h> #include <avr/wdt.h> #include <avr/sleep.h> #include <avr/interrupt.h> bool timer1 = false , led = true ; // Interrupt service routine for timer1 ISR(TIMER1_COMPA_vect) { timer1 = true ; } void setup() { // Setup output pins pinMode( 1 , OUTPUT); digitalWrite( 1 , led); set_sleep_mode(SLEEP_MODE_IDLE); // Setup timer1 to interrupt every second TCCR1 = 0 ; // Stop timer TCNT1 = 0 ; // Zero timer GTCCR = _BV(PSR1); // Reset prescaler OCR1A = 243 ; // T = prescaler / 1MHz = 0.004096s; OCR1A = (1s/T) - 1 = 243 OCR1C = 243 ; // Set to same value to reset timer1 to