Post by thread:[SX] Using an SX proto board in a car's 12 volt sy

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Hello all, I have an application in mind that would draw it's power from a car's 12 volt system. I was woried that it would strain the proto boards regulator as the 12 volts in car system while running can get up to 14 volts. I checked the specs on the LM2940 and it says it can handle an input voltage of up to 26 volts! My question is, if thats so why does the board specify a six to nine volt adapter? A 12 volt adapter should work fine right? Just wanted to check with the experts before I go out and fry a board! :shocked: Thanks, Jim W. :turn:

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Jim, The LM2940 might handle 26 volts, but not at it's maximum current (1 Amp). That would be (26-5) = 21 Watts of heat !!! At 9 volts it would be (9-5) = 4 Watts of heat, alot but probably okay with a heatsink. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:So, If I put a larger heat sink I should be OK with 12 volts? that should be easy and cheap! Thanks, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:See my edit above. It depends on how much current you are using. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:My circuit won't draw much current. I'll keep a finger on the heatsink. I could also put a little cpu fan over it if it gets too hot. But, I think I should be OK without one. Thanks again, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, cbmeeks wrote:Ok, I am curious...what are you making?

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Hi cbmeeks, I want to tell you now but I need to do a little more research before I blab about it. It's kind of a dumb idea (at least my wife thinks so.) But I think there might be a market for it. Others I've shown it to think it's a good idea (or, they are humoring me.) You will probably laugh. (like she did). But, give me a little while to get back to you. Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, c-isaac wrote:At least you got a reaction from your wife. If she were indifferent, you may need to think twice. Strong reactions, good or bad, are positive feedback. If some people love your idea AND some people hate it, it's a winner.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:If your wife thinks it's a dumb idea, that's better than a man thinking it's a good idea ;) When I got my LPKF PCB milling machine, my wife thought it was the dumbest thing she'd ever seen. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, cbmeeks wrote: [Quoting: "Basic Jim"]Hi cbmeeks, I want to tell you now but I need to do a little more research before I blab about it. It's kind of a dumb idea (at least my wife thinks so.) But I think there might be a market for it. Others I've shown it to think it's a good idea (or, they are humoring me.) You will probably laugh. (like she did). But, give me a little while to get back to you. Jim W. Hey, I had the idea of putting a small laser gun on a small robot car that had motion sensors. The car would pick up tiny bits of motion from insects (like roaches) and drive to them and shoot them. A tiny, laser shooting, roach killer. That would ROCK.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, brianbr wrote: [Quoting: "Basic Jim"]So, If I put a larger heat sink I should be OK with 12 volts? that should be easy and cheap!Thanks, Jim W. No you won't be that OK. I have used he SX48 with 12volts and it runs too warm over a period of time to my liking. Especially if its gonna be buttoned up some place or worse, under the hood. The easiest solution is to offload some of that voltage/power with a three to five 1N4000 series diodes in series with the 12V line, which will drop .7volts per diode. Rememeber that "12v" with regard to a car is a eumphemism for what in reailty is 13-14 volt system. The regulators put ot in the vicinity of 13.8volts. The batteries generally settle down in the low 12v range when the engine has been shut off. And it might not hurt to have a hefty choke in that line to beat down startup transients, as well as an overvoltage protection diode across the input. Automobiles are a very electronics unfriendly environment..

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Thank you Bean and Cbmeeks for your encouragement. The more I think about it the more I think it should be doable. What worries me most is that it isn't being done already so, there must be a reason. It's not rocket science. Thanks Brian, The diodes are an excellent idea. I'm not sure how hefty a choke I would need. Maybe I could scavenge one from an old car radio for testing purposes. Best, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:Having one or more diodes in series with the supply line has another advantage too: You protect the device against wrong polarity. This is why I usually put at least one 1N400x in series with the supply input.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, brianbr wrote: [Quoting: "earlier, I"]Automobiles are a very electronics unfriendly environment.. I just want to expand on that a tad .... not too many years ago, chips came in basically two flavors ... chips and mil-spec chips ... Now they come in more flavors and for the most part the top of the heap, that is, the most demanding specs, is not the military stuff, but ... yup, you guessed it ... chips destined for automotive use!

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:I was thinking that you could put a 7809 in front of the SX-48 and have that regulator dump the heat. Boy! Have I been wasting money.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Gunther, That is a fantastic point! I will stock up on those little critters Best, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Brian, Wow, I didnt know that. All this time I thought Mil spec was top of the line. Probably isn't much difference in spec. from military to automotive since both are subject to very extreme enviroments. Military might more robust in EMI surges I would think. Best, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:Kramer, You said, "I was thinking that you could put a 7809 in front of the SX-48 and have that regulator dump the heat." That's how I was going to tackle the problem originally. I glad I posted my question. This forum is a fantastic resource! Best, Jim W.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Steel wrote:Can you also just put a 9VZener in parallel to the circuit on the frontside, so that the Zener dumps anything over The 9V? Im just wondering for if my own circuits end up in that environment. It seems like a cheap fix to a noisy situation...

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, PJ Allen wrote: [Quoting: "Steel"] Can you also just put a 9VZener in parallel to the circuit on the frontside, so that the Zener dumps anything over The 9V? No (that is, No Way.) Zener current [I[sub]Z[/sub]] must be limited. Sometimes a Zener is used this way (in parallel with the input) when the greatest expected input voltage is "just a tad" greater than the Zener voltage [V[sub]Z[/sub]], intending to then clear a fuse as a result. Also, "pre-regulating" with diodes (pl.) isn't a panacaea, either (i.e. don't get carried away.) ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=144373#m145251 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Bongo wrote:I would think that the back emf caused by your transport's starter motor is going to cause you far more grief than the reg running a little warm. Would suggest a bipass diode as a bare minimum to some supply filtering.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:In critical applications I place a overvoltage protection diode, like a P6KE6V8 across the 5V supply (cathode to plus, anode to minus). Such diodes can dissipate peak power pulses of up to 600W at very fast response times. For example, I'm using them in an application where an SX controls a concrete saw, where extreamly high voltage transients can occur caused by a 400V, 16 Amps three-phase frequency converter. May be it's a good idea adding such a device to your automotive application.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jimbo wrote:When I think about all the elctronics people use in their car now it seems to me that my SX board should survive. I've seen people run their computers, cell phones and even TV's from the cigarete lighter. Seems to work for them. :freaked: For now I will try one of Gunther's P6KEV8 with some 4001 and a choke and that should hopefully get me by. :yeah: I have ordered a couple xtra proto boards just in case I'm wrong. If worse comes to worse I could break down and buy a DC-DC converter. :idea: Thanks, Jim W. :tongue:

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:Jim, please fins attached the schematic for a DC/DC converter. I'm using it in many of may applications, and it works great.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, transistortoaster wrote:

You can use the MC34063 switching regulator. It's real cheap. Frank ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=144373#m145899 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)