'Nother 'Lectrical Question

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Derek Harling	'Nother 'Lectrical Question		Lead	[-]
Registered User Posts: 736 02/25/08 16:02:32	Tags : None I've decided to use small LED warning lights - they come from Radio Shack and have a built in resistor so that they work OK with 12V (I think the LED itself is 9V rated). But - here's my question - I'll be using an alternator so the operating voltage will more like 14 or 15. Is this OK or am I in trouble? I tried asking the Radio Shack guys - waste of time. And of course I can't just 'try it' until I run the alternator - some weeks off yet. Thx in advance.
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David Ferguson	Re: 'Nother 'Lectrical Question	#1	[url]	[-]
Registered User Posts: 1290 02/26/08 04:36:49	If you're concerned, you could add a small 12V regulator to create the power supply for your LEDs. I think you'll be fine with a voltage 20% higher than the nominal value.
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David Arken		#2	[url]	[-]
Registered User Posts: 594 02/28/08 12:37:26	Or, just start up your tow vehical and put them across the battery, if they burn up you got the answer.... you can also just add another resistor. David
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B17overhead		#3	[url]	[-]
Registered User Posts: 155 03/23/08 13:41:24	If you know the exact current draw of the LEDs, you can calculate a dropping resistor. Easier and cheaper to hook up than a 3 terminal regulator. (Expected voltage-required voltage)/ current drain in milliampres= dropping resistor in kOhms Example: (14.5-9)= 5.5 V to be dropped 5.5 V /30 milliampres= 0.183 kOhm (also the same as 183 Ohms) Power rating of resistor in milliWatt is Voltage drop squared / resistor in kOhm For above example: 5.5^2=30.25 9/ 0.183= 165 mW Double that power for good resistor life and you have a requirement for a 370 mW total resistor power rating. That is the same as 0.37 Watts, so a pair of 1/4 Watt 370 OHm resistors in parallel should do it. with 500mW rating total. For resistors of the same value, parallel connection results in 1/2 each one's resistance in the resulting network and you double the power rating of each. I'll send you a spreadsheet to use, if you wish. The above example uses my wild guess for current rating. Chuck Voboril Last Edited By: B17overhead 03/23/08 13:57:04. Edited 1 time.
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Derek Harling	LED Voltage	#4	[url]	[-]
Registered User Posts: 692 03/23/08 21:50:24	Chuck - thx - but I finally found out that these Radio Shack LEDs are rated for 10-16v - so I quit worrying. I also tried them with my 14.4v drill battery with no problem. Derek
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Derek Harling	Just for kicks -	#5	[url]	[-]
Registered User Posts: 693 03/23/08 22:03:31	- here are some pics of the finished instr panel (IF I can load them)
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Clark Lincoln		#6	[url]	[-]
Registered User Posts: 713 03/24/08 13:32:35	Derek - VERY nice piece! A very clean combination of the new and the old. I have found in my racing career that what your IP looks like is very important to my level of comfort/confidence in the car. I can tell you that I would like to sit behind that little beauty... BTW - how about posting some shots of the rest of the car? Your thumbnail is hard to see. Cheers, Clark
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Derek Harling		#7	[url]	[-]
Registered User Posts: 694 03/24/08 20:39:12	Clark Lincoln wrote: I have found that what your IP looks like is very important to my level of comfort/confidence in a car. - Clark I completely agree with that - I find that I do NOT want to move my head much when driving at speed or at anywhere near the limit - hence I like my IP to be compact yet useful. I wouldn't like to admit how many mock ups I made starting with paper, then cardboard, plywood, then thin aluminum, then the final flanged 060 aluminum - but I still changed my mind on switch location after I'd had the plate welded and painted! Talking of switches someone asked me what the two horizontal toggle switches are for - they change what the gauges are reading - the left hand one from water temp to oil temp - the right hand one from oil press to fuel press (not sure I'll use that much - just seemed like a good idea to make provisional now). Oh - and the bottom readout is a text reader for pit signals - I don't like microphones in my ears.
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Derek Harling		#8	[url]	[-]
Registered User Posts: 695 03/24/08 20:47:39	- how about posting some shots of the rest of the car? Your thumbnail is hard to see. Clark - you're mixing up my projects - this IP goes in the F3000 which I figured I'd better get going before I'm 70. The sports racer is next - but I can probably still race that when I'm 80 - pics below - it is a Photon CanAm conversion based on a March 78/79B - yes the same Photon - originally done by Jeremy Hill (recently into F1000 etc).
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Derek Harling		#9	[url]	[-]
Registered User Posts: 696 03/24/08 20:49:01	- hmmmmmm - still can't get my text and pics properly juxtaposed.
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Clark Lincoln		#10	[url]	[-]
Registered User Posts: 714 03/25/08 12:56:30	So when did you expand your garage workshop to that amazing space?? And will I be able to text message you during a race? Clark
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Tom Clayton		#11	[url]	[-]
Registered User Posts: 2164 03/25/08 15:33:26	Oh - and the bottom readout is a text reader for pit signals - I don't like microphones in my ears. If he was willing, I wonder how well a microphone in the ear would work.
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Derek Harling		#12	[url]	[-]
Registered User Posts: 697 03/25/08 17:42:44	- Tom - can you speak up - I can't hear you - I've got a microphone in my ear. I meant speaker(s) of course. Actually don't some systems (not necessarily racing systems) use microphones in the ear? Not sure how they handle feedback.
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Brownslane.diasio	memory Lane	#13	[url]	[-]
Registered User Posts: 14 05/26/08 10:07:12	Derek!! I am more than familiar with that bodywork. I worked on that car when Franco built the original bodywork. That shape generated HUGE downforce!!! The Photon still has a couple of lap records, including fastest 2L at Mosport...ever! We ran that car with a 420R and contended for outright wins on more than a few occasions. Jeremy and I were roommates when he was running CanAm and I was running F-4 and F-2000. We used to build the Hart motors in our kitchen!! Funny smell out of that old dishwasher as we used it to wash our piston sets..... Jeremy is still around and faster than ever. He bought one of my production F-4 cars, and converted it into a continental. Some of you may remeber that car as it ran FC as the only bike powered car in the field. He ran in the east. John Mortinsen trid to ban that car from the runoffs three years ago, as I remember. Ahhh memories. Oh ya, the older I get the faster I used to be too!! hehe The car looks GREAT!!! I have lots of photos around as we built that car. If you need any reference information, please let me know, and if i don't have it, I'll talk to Jeremy. Regards, Tom in Toronto
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Derek Harling	Photon (CanAm 2L)	#14	[url]	[-]
Registered User Posts: 714 05/26/08 16:46:35	Hi Tom in Toronto - this is Derek near Detroit - actually Windsor (well it is near Detroit) Drop me an email to derek at lola7 dot com - include your tel no (day or evng) - would love to chat with you. I've spoken to Jeremy several times and met him once. By pure coincidence I also have the Ralt RT4 that he drove once at the 1982 runoffs -awaiting restoration like so much in my life.
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