Quote:
Originally Posted by meelis11
Hi,
I am Meelis …
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Quote:
Originally Posted by t vago
Keep us posted
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OK, I've fixed the blown Zener on my meelis board, so I've got that working. In my effort to now blow any more arduinos I decided to base my interface board on meelis' design which is a little different than the others. After reverse-tracing much of the board using Fritzing, I found this reference to the meelis design:
MPGuino schematic - MPGuino - Meelis P
I have some questions before I proceed -- I have fried some boards due to back flow -- (power coming in on the vss and existing on who knows what, the fuel injector or ground perhaps) -- do the extra components I mention below address this, and is that why I've been blowing boards, due to simple mistakes?
1. This design (l
ink) shows an electrolytic (or at least polarized) capacitor bridging the 7805 output and ground. All other designs show an unpolarized cap, and everything I've seen shows a nonpolarized ceramic cap in this spot. This cap is similar in function to the 330uf that bridges the input voltage and ground -- which is polarized. Shouldn't the .1uf cap also be polarized?
2. You have an 'extra' .1uf capacitor on the hot (12v) side of the 7805 regulator. So there's a 330uf polarized and 0.1uf nonpolarized. These are to smooth the circuit -- why is the 0.1uf cap here as well? I have seen situations (without the 0.1uf on the 12v input of the 7805) where there is proper voltage but the arduino browns-out (insufficient current). Could my lack of the 0.1uf cap contribute to this?
3. You have an 'extra' 50k resistor on the VSS input: input-->50k--->zener and 50k independently bridge ground). Why is this here? Is there a 12v tendency to cook arduinos on this circuit? (I've seen 12v come in across the vss at times)
4. You have a 0.01uf cap on the VSS -- why? All of these caps appear to be low-pass R/C circuits. Would this have settled down our other poster's Alfa Romeo that had close to 16*10^6 pulses per mile?
Once i know more I will start soldering together a prototype board with the 7805, and vss/fuel in channels. The design will be to use the adafruit button/LCD shield on an Arduino Pro Mini (and a tinycurtcits arduino) both of which are 3.3v 8MHz 328s. Then I'll post my results here.