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

Adding "Stereo Mixer" to Windows 7 with Conexant sound card

This procedure worked for my laptop (Thinkpad E530) with a Conexant 20671 sound card, but I suspect it will work for other sound cards in the Conexant family. I was playing with CamStudio to do a video capture of a Flash-based cartoon so that I can put it on the WDTV media player and play it on the big screen in the living room for my kids. The video capture worked brilliantly, but to do a sound capture, I needed to do some hacking. Apparently, there was this recording device called "Stereo Mixer" that was pretty standard in the Windows XP days. This allowed you to capture whatever was played to the speaker in all its digital glory. Then under pressure from various organizations on the dark side of the force, Microsoft and soundcard makers starting disabling this wonderful feature from Windows Vista onwards. So after much Googling around, I found out that for most sound cards, the hardware feature is still there, just not enabled on the software side. Unfortunately, to

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

Hacking an analog clock to sync with NTP - Part 5

This is how it looks after I have put everything together. The Arduino sketch is available here . The 2 jumper wires soldered to the clock mechanism are connected to pins D0 and D1 on the ESP-12 (in any order). When the device first boots up, it presents an access point which can be connected to via the PC or smartphone. Once connected, the captive portal redirects the web browser to the configuration page:     A custom field has been added to the WiFi configuration page to enter the current clock time in HHMMSS format. Try to set the clock time to as close to the current time as possible using the radial dial at the back of the clock so the clock will have less work to do catching up. In the config page, the HTML5 Geolocation API is also used to obtain your current location (so if your web browser asks if you would like to share your location, answer "yes"). This is then passed to the Google Time Zone API to obtain the time and DST offset of your time z