i dont think this really applies in this case though, where we have hundreds of amp-hours available and we're only draining maybe 2a or so at any given time. the battery voltage would be a good indication on charge state. im not sure what the lowest voltage my truck will start at, but i would think it needs around 12v minimum.. especially on the colder days. thats why the m2's current 11.1v cutoff has left me stranded numerous times now... although i think i finally solved that problem by just going with the 1-min hardoff.
Originally Posted by nobb
A typical passenger vehicle might only have a 50 amp hour battery. Even a large pickup truck might only max out with a stock 100 amp hour battery. Definitely dont have "hundreds of amp hours available."
Ive got a system that's supposed to be low powered since it's a Via 2.0ghz based system, but I still measured the power consumption to be 6 amps which is a considerable amount in relation to the total amp-hours available. 12V or 11.5V is a good loaded voltage to cut off the system because once you unload, then the battery voltage is most likely going to jump up a bit. However, by definition, 12V unloaded (steady state) is practically considered to be 100% discharged for a lead acid.
No updates & pm..
No, the project is not dead.... I have just been really busy lately and out of town a bit. I apologize to all who have sent me their information so far as I have not had a chance to send out any PICs yet. I do still intend to do it soon.
Last night I finally started fabricating the bezel for my monitor so I will be starting a build log soon and that will hopefully keep me motivated to make some progress.
I also took some current measurements with my code and with the mini-box code during low power state. As expected, my code does use a little less power, but it was not for the reason that I originally thought. I measured the power in the hard-off configuration with the PIC in the M2 as well as the power of the microprocessor alone in a breadboard in the same configuration. My M2 draws about 76 mA with the mini-box code and about 72 mA with my code if I remember correctly. What is interesting though is that the PIC actually draws a little bit more power with my code, I assume because of the faster clock speed. I don't remember what the actual current draw of the PIC itself was, but it was negligible compared to the rest of the board... a few uA.
What I think this means is that I configured the pins a little better in the low power state to minimize current draw from the board, but it looks like most of the current is from parts other than the microcontroller and may not be able to be eliminated without cutting the 12V constant to the M2 with a relay or something. I would like to make a few more measurements and try to see which parts of the circuit are using the power if I can to better understand what we can do to maximize battery life. I am also working on a few tweaks to the voltage detection scheme to take advantage of the voltage difference between when the engine is running (~13.8V) and when it is not (~12.6V). I am putting a couple of amplifiers in my car and I don't want the computer to give me a shutdown when the subs hit if the voltage drops a little bit, though I am going to try and prevent the voltage from dropping...
EDIT: I am going to ask people to please wait until the code has been tested a little bit before asking any more for chips. If you have already received a PM from me, I will send you one as promised. Otherwise, please be patient... I just don't want to send out a bunch of chips that have some small bug that might be discovered in a system other than mine. I am sure people will like the functionality of the code, and I promise it will be available soon!
Any word on when/if these will be available?
My goal is to delay the amp turn on to stop the PC beep.
OK, I am reviving the thread!!! Yay!
First, let me apologize to everyone interested for the delay in this process, as I expected to install my carPC a LONG time ago.... It took longer than anticipated mostly because I decided to go all out on sound deadening and audio and am DIY'ing everything.
I have finally had the chance to install my computer in my car (build log soon to follow) and have had my code running in it for a couple of weeks with no problems, so I think it is ready to send out to other people. Here is my plan for getting it out to people:
I have PM'ed the people on my list from earlier this year that I promised to send test PICs
I hope they will try them and post their feedback on the thread
After it has been tested by those few people and any (hopefully none) unforeseen issues are resolved, I will set up a way for people to order through paypal
I am planning on asking 10 dollars to cover the cost of the hardware, shipping, and PIC programming time, and then if you feel that it is a big improvement in your case, you may donate any additional value that you think it is worth
We will just go from there for now, as I am waiting to hear back from my promised testers...
Glad you're back, blu, and looking forward to hearing the results and getting access to a part.