welcome to my noob car blinking leds project :o)
is it useful ? right now of course not! but my goal is to have fun with a silly thing and learn :-)
i only did digital breadboard prototype designs since now and ... a lot more software programming :oP
so one goal for this is to learn few new stuff from hardware production point of view.
so for that silly project basicly can be a test bed from producing a home prototype to probably producing a really small real pcb production run.
of course i 'll have many many questions :o)
feel free to participate of course.
so there's the starting point
im planning to used
voltage regulator 7805CT with 2 capacitors
one silly push button who will be software debounced.
few leds (who will be at somepoint replace with something who will make me an hyper rich man ) :oP
and a pic12F1840 running internal clock .
the pic is kind of overkill but has really interesting spec and a lot of ram space to play with.
(http://http://i1114.photobucket.com/albums/k539/n45w73/dev/z0014a.jpg)
so here my question
can i used just a power reg like that to power my small board from 12v car batterie
any other kind of filter need ?
i surely dont want to fry my little PIC !
any pros and cons on this little PIC ? ( im swaiting for them they are in the post somewhere)
next step, producing a perfboard and plug it on !
:o)
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Added stuff
Parts Links
7805 http://http://www.onsemi.com/PowerSolutions/product.do?id=MC7805
1N400x http://http://www.fairchildsemi.com/pf/1N/1N4007.html
pic12F1840 http://http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en549758
P6KE18a http://http://www.onsemi.com/PowerSolutions/product.do?id=P6KE18A
can i used just a power reg like that to power my small board from 12v car batterie
any other kind of filter need ?
i surely dont want to fry my little PIC !
I would worry more about frying the vreg. This isn't my area, but I've read enough of rsdio's app notes related to automotive design to get the feeling that there are some nasty spikes in car systems. Maxim makes parts with protection against 72volt spike and other nasty stuff. See for example this one: http://dangerousprototypes.com/2011/06/ ... lt-spikes/ (http://dangerousprototypes.com/2011/06/04/app-note-automotive-power-circuit-handles-interruptions-and-72volt-spikes/)
any pros and cons on this little PIC ? ( im swaiting for them they are in the post somewhere)
next step, producing a perfboard and plug it on !
With the low pin count chips you lose 5 pins to programing and power, leaving only 3 to do real work. If you can live with that give it a shot.
with 8 pin pics you have 2 for supply, 1 input only (mclr) and 5 input/output. So it should be enough for your application.
You should consider the 12f1822 as it availability is much better (for soic that is :D not DFN)
[quote author="ian"]
can i used just a power reg like that to power my small board from 12v car batterie
any other kind of filter need ?
i surely dont want to fry my little PIC !
I would worry more about frying the vreg. This isn't my area, but I've read enough of rsdio's app notes related to automotive design to get the feeling that there are some nasty spikes in car systems. Maxim makes parts with protection against 72volt spike and other nasty stuff. See for example this one: http://dangerousprototypes.com/2011/06/ ... lt-spikes/ (http://dangerousprototypes.com/2011/06/04/app-note-automotive-power-circuit-handles-interruptions-and-72volt-spikes/)[/quote]
yikes ! i wish my car isn't spiky like that ! (but there is some rumors saying HID on car are really spiky)
i didn't take measurements yet but i think a batteries car can "float" from 11v to 15v...
maxim design could be good if you need something really foolproof ! seem also good against brownout !
here also some info on reading vreg datasheet from Dave EEVBLOG
http://http://www.youtube.com/user/EEVblog#p/u/30/ICQXqVy3Hpc
[quote author="Sjaak"]with 8 pin pics you have 2 for supply, 1 input only (mclr) and 5 input/output. So it should be enough for your application.
You should consider the 12f1822 as it availability is much better (for soic that is :D not DFN)[/quote]
yes this is my first dilemma doing nothing useful on little space with few pins and more ram.
or doing more nothing with more pins taking more space but with a potential bigger/costly production board at the end... (im planning to use dip, cause im able to solder that, not sure about smd )
im usually thinking bigger is better :o) so i also ordered few 16f1825 just in case :-)
[quote author="voidptr"][quote author="Sjaak"]with 8 pin pics you have 2 for supply, 1 input only (mclr) and 5 input/output. So it should be enough for your application.
You should consider the 12f1822 as it availability is much better (for soic that is :D not DFN)[/quote]
yes this is my first dilemma doing nothing useful on little space with few pins and more ram.
or doing more nothing with more pins taking more space but with a potential bigger/costly production board at the end... (im planning to use dip, cause im able to solder that, not sure about smd )
im usually thinking bigger is better :o) so i also ordered few 16f1825 just in case :-)[/quote]
You'll be amazed what you can solder :) A couple of month ago I never suspected I could solder 0603 by hand, and was surprized I actually could.
here some thought about electric noise/spike
i am a bit afraid to fry the vreg if i put nothing between it and the car batteries,
so i'm going to use a VPS (voltage spikes suppressor) probably something like
a P6KE18A who is fairly inexpensive...
http://http://www.onsemi.com/PowerSolutions/product.do?id=P6KE18A
i might get few of them, from a local distributor, tomorrow and torture them :oP
Using a 7805 (I assume you'll gona use +5v) can handle IIRC input voltages up to 30-35V, which is enough for automotive applications. Downside of lineair voltregs is they dissapate the excess voltage as heat, so add a big heatsink.
With 15V in and 5V out, using 1A the voltreg is dissapating (15-5)*1=10W.
i read few application note on TVS, transil etc ... and i have no scope for testing my car ...
the 7085 seems to have one cutting at 35v but for few cents i thrown in another tvs, on a prototype why not ...
yes using full 1A will make this thing pretty hot...
right now blinking 2 leds and a push button, everything run in my car and used 18mA and it just warm.
i know i commit a crime sort of ... a pic who needs really no current and some noob pieces who sink a lot of it :oP
so i guest for future project i will investigate those stepdown buck regulators maybe something like the LM2576 :-) they surely are much more colder (and cooler) than 7805 :-)
any hints on that ? ;-)
Maybe this will help?
High-Voltage, 2.2MHz, 2A Automotive Step-Down Converter (http://http://dangerousprototypes.com/forum/viewtopic.php?f=42&t=921&start=75#p24829)
[quote author="rsdio"]Maybe this will help?
High-Voltage, 2.2MHz, 2A Automotive Step-Down Converter (http://http://dangerousprototypes.com/forum/viewtopic.php?f=42&t=921&start=75#p24829)[/quote]
when i click on this it goes in some void space .... but maybe it is just me :oP
Sorry for my slow response.MAX16974
High-Voltage, 2.2MHz, 2A Automotive Step-Down Converter with Low Operating Current2A Automotive Buck that Meets OEMs' Tight Power Budgets
- Wide input voltage range (3.5V to 45V) allows seamless operation from cold crank to load dump
- Low quiescent current meets tight power budgets
- High-frequency operation eliminates AM-band radio interference
More Info (http://http://www.maxim-ic.com/datasheet/index.mvp/id/7001)
here what is happening :-)
i build a prototype on a perfboard and im please everything blink fine since a week :o)
(http://http://i1114.photobucket.com/albums/k539/n45w73/dev/pcbperf.jpg)
but now it is time to build a pcb and ... in a near futur sell zillions, and make zillions of $ ! :oP
so here my first try with eagle ( i never play with that before !)....
(http://http://i1114.photobucket.com/albums/k539/n45w73/dev/pcb1.jpg)
now i got some questions ....
where can i find diode specific models, i need 1n4007 and P6KE18A.
i used 1n4004 and generic P6KExx ... i also want vertical mounting models like what i use for my resistor ...
i guest i will have to build it someway, but how, is there some example ?
if i use the flat on board mounting model for my regulator, will eagle make automatic back pad for a heatsink ?
it's all for now, time to eat :O)
I think you could better use a normal heatsink made of aluminium (assuming a 14V car-input)
If you use a flat version of the TO-220 there would be a pad that is a small heatsink. You can use the polygon or square tool to extend this pad (and the thermal capabilities).
the package of a 1n4001 is the same as 1n4001..1n4007. IIRC there are also some upright versions of these diode somewhere in the standard library. If they don't exist, you can add them yourself (easier then you would expect ;) ), there are several tutorials on the net. I got most of my eagle library skills from the sparkfun tutorial about eagle libraries: http://www.sparkfun.com/tutorials/110 (http://www.sparkfun.com/tutorials/110)
learnt a few tricks after this, but the idea stays the same :) If you need help with making your own footprint please start a topic, we are here to help.