power distribution

Before I go any further, I would just like to say how profoundly pleasant is this experience! I very much enjoy reading these posts - where we just 'chat about stuff'...and pick up some really useful info along the way. Gentlemen - THANK YOU for creating a respectful & interesting forum. A fair bit of this is well beyond my experience/knowledge. When I got into RC [collective pitch] helicopters, I quickly discovered that my forte was most definitely fabrication & repair...as opposed to actual flying I continue to gamely make a go of it (flying, that is) but let's just say that my flying skills produce a disproportionately large amount of opportunity for my - ahem - other skills. This carries over into the current (nice one, eh?) adventure. I take great pride in the fabrication -- and have fun doing it -- but I am not as strong in the theory. That said, I am not so ignorant that I would blindly fire something up just because I'm proud of how nifty it looks! And that's why I am here; to bolster the areas of my skillset that I know are lacking. (Thank goodness I am rakishly handsome; clearly you fellows -- as gentlemanly & knowledgeable as you are -- have nothing to offer in THAT arena.) But I digress. I have a handful of barrel-style fuses on hand for the primary feeder - I shall insert one in that line within 12" of the battery. This box may not go in for a bit, because it is brutally cold here (and to my ongoing frustration I still cannot find an indoor workspace) PLUS the LED lightbar is not even installed yet. Meanwhile, the single HID and the twin 55's are working perfectly. Hopefully it'll improve enough soon to get this done, since the completion of the enclosure has seen the lion's share of the job taken care of in the comfort of my basement!

I realize that "dividing by 10" builds in a safety factor (which isn't necessary, but isn't hurting).. io just want to make sure that folks realize Ohm's Law will tell you what you need... .. and if you're not using the actual input voltage (nominal, or measured) in that formula, you're not using Ohm's Law. I don't want to take this convo off the rails (again), though, so I won't go further on that. Suffice to say, the OP has done a very good job of this project, and I can't wait to see everything finished. I'm off to see if I can find some more high-amp blade fuses, as this conversation has inspired me to build something I've had in mind for a while!"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

oldspark wrote: To address some of burntkat's comments... I explained why the 10 factor is used instead of 12. But it is also a simple initial design approach which often turns out to be quite accurate in practice. For the exact design you would not use 12 (I can't think of anyone that would use 12V as the design voltage for 12V automotive etc systems), but 12.7, or 14.4, or whatever minimum voltage is applicable (11.6V, 10.5V, 8V etc) and also factor in any inefficiency, and then whatever overhead you want. Plus allow for manufacturing tolerances, temperature, etc.

And the very moment you get out of a low-voltage realm, all of that goes out the window. If we're going to share knowledge so that others may learn, let's teach them properly. Example: Going with the "/10" rule, someone learns the above and applies it to their automotive build. Outstanding, wonderful, works great, lasts long time. I fully support it. But once you step outside the low-voltage realm (which is going to happen in automotive use, thanks to hybrids and so on), you end up with the wrong answers entirely. It's dividing by 10 versus dividing by the nominal voltage of the system. If you're going to practice engineering, practice engineering, not "about right, wild-ass guess"."Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

oldspark wrote: Re CBs - it costs under $10 for a (self resetting) ATS CB up to 30A (or mini-ATS CB up to 20A) which - being ATS - generally has no packaging (housing) concerns.

I am curious about these. I wasn't aware there are self-resetting CBs in the same package size as an automotive blade fuse. I've looked for "ATS CB" and am finding refrigerator-sized units. Obviously I am not searching for the correct thing. Educate me? :)"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

Some circuit breakers for viewing. http://www.waytekwire.com/products/1366/Circuit-Breakers/&Type=Blade-&Reset-Method=Type-I---Automatic&Mounting-Style=ATO---ATC-Blade http://www.delcity.net/store/ATO-:-ATC-Blade!Style%3Cbr%3E-Circuit-Breakers/p_151 Appears there are three types of circuit breakers: Type 1, 2, and 3. Type 1 is described as automatic rest, 2 Modified, and 3 Manual. While they do fit into an ATC/ATO fuse holder, they are significantly taller in profile. So the base is of the same size of course.

Thanks for that, Ween- I didn't know these existed. Unfortunately, owing to the profile, the packaging is still an issue. But they're certainly much smaller than I expected."Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

burntkat - I am talking engineering, not 'wild guesses'! Talk about a mob (Engineers) that use ROTs (yet unfortunately often blindly so)!    And who's talking about "getting out of a low-voltage realm"? I am talking about a common ROT used for 12V automotive electrics. I am not talking about calculating the current for a specific voltage and load. Not meaning to sound facetious, but is your unawareness of ATS style CBs indicative of limited automotive electrical engineering experience? (Don't worry - I often lack such awareness despite being expert in certain fields - it's one of the hazards of using ancient learnings with deliberate (modern) ignorance, else boredom.) That reminds me - I referred to ATS types fuses - I meant ATC (or ATO?). I normally just refer to them as blades (and mini-blades and micro-blades). Typical me - despite designing with discrimination (i2t profiling), I'm still sketchy on their technical name. As usual I found a few such as ATO/ATC Blade Style Universal Circuit Breakers (only $3.84 each!) using 'blade circuit breakers' in google images. Not that I found the ATCs that were even smaller than that sample which are larger and can have 'stacking' issues (and I don't mean the micros or minis that Ween linked). Note that the div-10 is not for any safety factor per se, it is simply a ROT that is used either when estimating input current based on output power (amps, HIDs, converters etc), or a load current that factors in the voltage variance of a vehicle. AFAIAAware it is an old rule from the days when 12V vehicles regulated to 13.8V and hence 13.8V was the "standard" voltage used for ratings - eg, a 55W bulb meant 55W/13.8V = 4A (3.98A) - not that they had constant current or constant power back then (did they?). I don't know if there is a 'standard' voltage these days (that's my blissful ignorance) but I see 14.4V is often used, but so too 12.0V & 13.8V. Of course input voltages are irrelevant for HIDs and certain LED lights. (And should be for big amplifiers yet many seem to imitate resistive loads according to their specs, but that's an old conversation.) But the div-10 is not a final design. It is a first cut guesstimate. The final design needs its sanity check and confirmation against the user's max & min voltages with whatever safety margins or overheads are desired. However it is amazing how often the div-10 calcs agree with the final design, largely thanks to rounding up to the next preferred value of fuse or cable etc. Note too that I am using div-10 because there has been no specification of what the voltage range is, nor actual load input powers or currents (as measured - not based on nominal specs). If you still don't understand what the div-10 rule is about, maybe you could give an example of your design - eg, for ronemca's 50W HID (or 120W LED) - and then we compare? That's provided ronemca doesn't object - I'd hate to see his thread get too long.

ronemca wrote: ... I quickly discovered that my forte was most definitely fabrication & repair...

Oh man I like your style. (And that's just mentioning ONE example!) Damn it, maybe I will have to read previous posts in this thread. Bluddy Canadians - far too much in common with us Aussies (some unfortunate, but hey - I concentrate on the good things!). Thanks ronemca for your comments. I admire those that do see the learnings and the discussion. But to still see it after pages of garble which sometimes seems to be or is contradictory, or merely mentions/scrapes some complex issue.... For my replies I advise to rereading and often to reread in sections ie, one bit or concept at a time. I do the one reply that has it all - just like books etc - however I leave the chaptering up to the readers. But whereas books are planned... But I'll break for now - I need to visit a wrecker for my repairs. No, not breakages - I'm obviously a far better flyer than you - but due to the damned pathetic quality of my car parts. Honestly, you'd think a wiper assembly manufactured and fitted in 1964(CE) would last longer. It's not as if the wipers have wiped the road for the >1 million miles that the underbody has. Oh well, they used to call it Jap Crap back then. I'm now beginning to see what they meant. In the mean time I hope my our your humor improves. Yours in all sincerity. Peter. PS - I simply cannot allow the 2nd last line (above 'Peter') to pass as is. 'Yours faithfully' or 'in good faith' may be acceptable, but certainly not 'sincerely' if it is taken to include other than my first 3 paragraphs. I may at times assume too much familiarity and risk misunderstanding, but sometimes that and honesty cannot be risked.

Have at it, gentlemen! Let fly the wurdz uv wizzduhm. While I can hardly get any more good looking...I can certainly improve my knowledge base. Besides - I'm having fun! With flying season well & truly over...I need the distraction. That said, I am not now -- nor do I expect to become -- involved to quite the degree that is being hinted at in this thread. (Ms. Kate Beckinsale occupies far too much of my attention here at the manor) But if -- with the guidance and discussion that is being kindly offered here -- I can get this rig up & running without burning anything up, I will be a happy camper. [thumbup]

OK, I just read the entire thread. Gents, I am VERY disappointed - there was not as much humor as I expected tho IMO Ween takes the prize with Diode School, 101 Semiconductor Lane (I thought it was Semiconductor Tunnel, Ling). However the experience and tips made up for that. To see others that know of bad crimpers, soldering, etc etc. And ronemca - you nailed the freewheeling or spike-protection or snubber diode across the relay coil. That was a quick learn indeed - you seemed to grasp it easily. FYI - my summary is that the diode is normally reverse biased (does NOT conduct) so it has no effect on the circuit, but when a coil releases (is de-energised) it produces a huge -ve spike so that the normally +ve end (86) is more -ve then the GND or -ve end (85), and that can wreck attached electronics. It also gives a nice kick if you'd like to put a finger on each of terminals 85 & 86 when you de-energise the coil. Anyhow, that's when the diode conducts and hence shorts that -ve pulse. And 12V/24V coils generally generate spikes up to ~200V, and hence 1N4004 (400V) or 1N4007 (1000V) diodes are used. 1N400x diodes handle 1A. The general guidance is that the diode should handle twice the current of the coil, and since most automotive relays like we are using are 250mA or less (hence needing a 500mA diode), the 1N400x series is fine. So instead of generating a back-EMF (spike) of ~100V to -300V which will kill most semiconductors, it is snubbed to a mere ~0.7V which is safe. And as Ween wrote, will also reduce noise. (Good one Ween - I rarely think of that even though I had dash lights that would flash on when I turned off my highbeams.) Incidentally, I hate relays with inbuilt diodes (variou$ reason$) and instead prefer to incorporate 1N4004/7s in the harness or socket. And tho I usually don't bother because mine are mechanically switched, I may start including diodes as standard for the sake of noise suppression. As to relays with inbuilt snubber resistors, IMO why bother - go it properly. And that's a good segway... You all like to do things properly. And over design. (I won't say over-engineer...) IE - ensure it works, remains reliable, and is reasonable future proof. YAY! But like I said - impressive stuff. I thought long threads meant trouble. This is an (IMO rare) exception. Ok, some confusion about coil diodes, but so what? And I was worried about a metal case housing wireless receivers... I like Ween's feeder cable splitting (1-8ga = 2-11ga = 4-14ga) as well as other great bits. And burntkat has so many comments that hit home. (Obviously you must have flamed any cat deliberately - it certainly would not be accidental!) And as to Sir OP - a quick learner with an interesting expression of humor. Anyhow, I'll get back to burning some servos I got from the wreckers... Maybe after some wine. (It was a warm sunny day until the smell of bushfires rode in ahead of real gusty chilly winds and black storm clouds that were quire scary. If only I had a drink for the road... (no! never.).)