Operational lifetime counter IC? - Page 1
Forum section: electronics / projects

author: mfarver
author_rank: Newbie
timestamp: May 22, 2015, 03:26:31 pm
content: Does anyone know of a IC that automatically does a "runtime hours" or powered on time counter? Or an "odometer on a chip" solution?Everything we log for maintenance purposes is based on operational time. I don't really need an RTC, and I can't put a battery into the design anyway. It isn't too hard to implement this using a small micro with some onboard EEPROM and a reasonably accurate onboard clock. Still it would be a great to be able to claim to management that there was a one chip/tamper resistant solution for this.Seems like this is something that should exist, but I haven't found anything.

author: N2IXK
author_rank: Frequent Contributor
timestamp: May 22, 2015, 04:20:25 pm
content: http://www.kep.com/productPages/counters-timers-ratemeters/K198-PCB-mount-hour-meter.htmlBack in the pre-ROHS days, the usual solution for this was a little gizmo called an "Indachron", which was a tiny capillary tube filled with mercury, with a little bubble that would slowly move along the length of the tube over the life of the device. A scale similar to a thermometer gave the runtime indication. These were used on a lot of industrial/broadcast gear subassemblies like VTR headwheels or large xenon arc lamps which required replacement after X number of hours of service, or which had pro-rated warranties based on service life before failure. A datasheet for these things is available here:http://datasheet.octopart.com/120PC12625-Curtis-Industries-datasheet-27869806.pdf, but due to the mercury content, the product line has apparently been discontinued. Some distributors still have them in stock, though.

author: nctnico
author_rank: Super Contributor
timestamp: May 22, 2015, 04:27:24 pm
content: A simple 8 pin microcontroller with internal EEPROM can do this. Be sure to write the EEPROM in a circular loop so you can enhance the lifetime of the eeprom. If you have the microcontroller transmit the run time counter as a UART serial format you only need to connect a UART interface to read the data (9600 baud can bet bit-banged so you don't need a real UART).

author: mfarver
author_rank: Newbie
timestamp: May 22, 2015, 04:51:13 pm
content: The subassemblies (which are field swappable) all report runtime back to a master diagnostic module so the counter needs to be digitally readable.

author: ajb
author_rank: Super Contributor
timestamp: May 22, 2015, 06:24:02 pm
content: A 6- or 8-pin micro would be a good solution, but may be problematic depending on how tamper proof you need it to be. While most micros have some provision for securing the program memory, I'm not sure what your options are for preventing the EEPROM from being erased. Usually you're trying to prevent data from being read from memory, but want to be able to erase it at will. You have the opposite problem. I think on an ATTiny13, for example, if you set the lock bits to mode 3 and set the EESAVE fuse that might do the trick--but it might still be possible to unlock and erase the EEPROM via high voltage programming if you have a really determined tamperer.

author: technix
author_rank: Super Contributor
timestamp: May 22, 2015, 08:22:51 pm
content: If your board already have a MCU in it, use its internal EEPROM, or whack a 24C02 on it which is cheaper than a separate MCU.If your project is some kind of IoT gear that can access Internet, you can do some Apple-style serial number registering (which is how they can keep track of your device's' warranty without asking you for a proof of purchase date.)

author: Fumo
author_rank: Newbie
timestamp: October 24, 2019, 03:38:57 pm
content: I know this is an old post, but I was looking for the same thing and came across this post first in my search. Eventually came across the DS1683 from Maxim that seems to do the trick.https://datasheets.maximintegrated.com/en/ds/DS1683.pdf.