basic l.e.d. wiring

Could you possibly do a mock up of the connections.. This is as far as i have gone..

Remember your talking to someone who is ... what is the term.. still ignorant.. but learning..

ajm

okay.. let me repost.. too bad i cant delete the last one..

I figured I had just missed something, which i think i did, but I re-read everything you posted and all the information was there except for what I am posting now.  See pic below:

So this is where I am at.. Had I taken the time to read your post earlier.. or had the option to delete the last picture.... I would have.

ajm

Almost... The (MOS)FET should be in series with the LEDs. And (I think...) its D & S swapped (S to GND, Drain to the -ve end of the LEDs or their negative-end resistor). And maybe include an ~1M to 10M resistor from the MOSFET's Gate to Source (GND) to ensure it is turned off if open-circuit (eg, when the PIC's signal for the MOSFET's Gate in "not on" (ie, an open-collector output as opposed to both pull-Lo and pull-hi to +12V). Unless you do want it fully on (with bright LEDs) in in case of PIC/circuit failure? The FET could be omitted initially (and its D & S pins shorted out (joined) with an temporary wire link) so that you get the "straight supply" voltage with no FET D-S voltage drop. You can then confirm max LED brightness and optionally the current. That then confirms LED operation without involving the FET. If that's ok, add the FET and confirm its on-off by a wire - maybe with an inline resistor to its Gate (100k?) - being touched to +12V (on) and off (GND). Probably too ad a resistor between the PIC output and the Gate. Anywhere from (maybe; it depends the PIC's specs) 100R to 1k or 1k (Ohms). Its function is to prevent PIV damage by limiting output current (or inward "sink" current). [ eg, the 555 timer has a 200mA source/sink limit. Hence a resistor of at least 82 Ohms from its pin3 (output) to anywhere on the circuit (ie, +12V & GND) protects it since I=V/R = 12V/82R = 146mA - well below it's allowed sustainable 200mA. ] The current to drive a FET Gate is nano-Amps; eg I=V/R = 12V/12nA = 1GigaOhms. Hence 1M should be fine, but it seems many chose a common value 10k or 1k. [ Better not too high a resistance as weak electrical noise could interfere and cause fast analog switching (instead of our "digital" full-off and full-on (even when "modulated" by the PWM which is "digital" but with varying on times. ] Then 2 stages. First the initial basic and "fall back" circuit without the PIC. Top of LED string (ie "top" = +ve LED end) to +12V. -ve Kathode end of LED string to the bright resistor (820R? 680R? with its other end to the added dim resistor AND MOSFET Drain else relay contacts (ie 30 or 87). MOSFET Source or other relay contact (ie 87 or 30) to GND (0V). The remaining (bottom) end of the added dimming resistor also to GND. With the FET off or with relay contacts open (ie, the relay is de-energised), the LED current flows thru the LEDs and both the bright and dim resistors and is hence DIM. The FET-ON or relay closed bypasses the dim resistor to GND, hence current thru LEDs thru the bright resistor then thru FET or contacts to ground, hence the LEDs are bright. IE - FET or relay turned on for BRIGHT LEDs. The 2nd & final stage is with the PIC providing bright/dim PWM and flashing control etc. Relay contacts are replaced with MOSFET (connected as above). MOSFET Gate (with say a 1M pull down resistor to GND) thru (1k?, 10k?) resistor to PIC PWM control signal output. Remove the dim resistor. [Pull at least one leg, or cut its wire for later fallback, or use a switch or (maybe - subject to corrosion and vibration) jumper or header pins (yeah - if current rating ok...) if you want easy swapping between PIC & "dumb" version.] Or you could leave the dim resistor in place, but then the LEDs will not extinguish unless the LED +12V (or GND) is removed. It will PWM etc between fully bright and taillight dim. Voltage regulator: Only one is needed to power the PIC itself. Inputs etc do not need "voltage regulation", but they usually cannot exceed the PIC's 0-5V. But 12V etc inputs can be scaled down using a voltage divider (whose output is proportional to input as the on the ratio of 2 resistor). For a car there might (should?) be some extra protection, but that can be added later (caps, maybe a resistor & zenor, or MOV (for spike protection). I'd suggest the common 7805 5V 1A regulator (in a TO-220 3 terminal package) for ~$2. The slightly cheaper and much smaller 100mA 78L05 could be used, but maybe the easier to handle and larger 1A version for the initial prototype.    (An adjustable & thermally self-protecting 317 can be also used by adding 2 resistors, but maybe KIS it now & use the preset 7805 5V regulator._ Both 780x & 317 regulators handle a max ~+35V supply depending on current and heat-sinking. The final thing is grounding, the PIC should be well grounded to the FET, but the FET to LED assembly;s GND should be separate and heavier, but that's probably thru the GND body/chassis anyway. The 7805/PIC +12V can be on the same circuit as the stop and tail-lights (are your lights or brakes on without IGN? Maybe then power the PIC from +12V, or diode feds from IGN +12V and brake-on +12V and tail +12V, so if any turn on, the PIC (boots up) & operates.    

Good afternoon Oldspark.

I finally figured out why I couldnt read Current.. Long story but took 2 days to realize the issue.. (broken terminal on meter)

Readings for the LEDs:

.021 Amps

~2.027 Volts (I'm not sure where the seller on ebay got ~3.4-3.6V for red..  he also claims 100Kmcd

I just finished wiring up 6 LEDs in a series and they are all sitting at 1.994 V except for one at 2.037V( I dont think I have to worry about a tenth of a Volt) 

Currently waiting for all my stuff to come in that I know I need..

I will post an updated schematic tomorrow.

ajm

LOL - always trust manufacturer/supplier information - NOT! That's good too - I was wondering if I was some sort of idiot claiming ~2V when they reckoned ~3.5V. Your LEDs look well matched. I think 1/20th of a Volt (0.037V) is pretty good. So that's 6 in series = 12.0V at ~0.2A = 20mA. Assume 20mA is their rated DC max, so drop 2.5V (14.5V-12.0V) @20mA => R=V/i = 125R => 120 Ohms (preferred value) else 150R. So 120R for your "bright" resistor with 6 LEDs in series. You'll have to decide the number of LEDs. All strings should have the same number of LEDs (so that none are different) but that depends if the total number is divisible by n x s, ie the number of LEDs in a String times the number of strings. You might find that 5 or 4 in a string works better... If bright = 120R I'd assume dim would be around 470R, hence add a 470-120 = 350 => 330R or 390R resistor in series with the 120R. That assumes my topology where bright & dim resistors are in series and the MOSFET or relay contacts short out (bypass) the dim resistor when brakes are on. But if you are going to PWM them instead, then just the bright 120R and through the FET which is either fully on for bright, or PWM'd for dim, of off for off. Note that those resistors are for EACH string of 6 series LEDs. If you change the number of LEDs, the resistor value(s) needs to be changed.    But the FET (if used) is connected between the common of all strings (ie, join their ends together - one end to +12V, the other to the FET) with is other side (Source) to GND. Good luck.

oldspark wrote: Almost... The (MOS)FET should be in series with the LEDs. And (I think...) its D & S swapped (S to GND, Drain to the -ve end of the LEDs or their negative-end resistor). And maybe include an ~1M to 10M resistor from the MOSFET's Gate to Source (GND) to ensure it is turned off if open-circuit (eg, when the PIC's signal for the MOSFET's Gate in "not on" (ie, an open-collector output as opposed to both pull-Lo and pull-hi to +12V). Unless you do want it fully on (with bright LEDs) in in case of PIC/circuit failure? The FET could be omitted initially (and its D & S pins shorted out (joined) with an temporary wire link) so that you get the "straight supply" voltage with no FET D-S voltage drop. You can then confirm max LED brightness and optionally the current. That then confirms LED operation without involving the FET. If that's ok, add the FET and confirm its on-off by a wire - maybe with an inline resistor to its Gate (100k?) - being touched to +12V (on) and off (GND). Probably too ad a resistor between the PIC output and the Gate. Anywhere from (maybe; it depends the PIC's specs) 100R to 1k or 1k (Ohms). Its function is to prevent PIV damage by limiting output current (or inward "sink" current). [ eg, the 555 timer has a 200mA source/sink limit. Hence a resistor of at least 82 Ohms from its pin3 (output) to anywhere on the circuit (ie, +12V & GND) protects it since I=V/R = 12V/82R = 146mA - well below it's allowed sustainable 200mA. ] The current to drive a FET Gate is nano-Amps; eg I=V/R = 12V/12nA = 1GigaOhms. Hence 1M should be fine, but it seems many chose a common value 10k or 1k. [ Better not too high a resistance as weak electrical noise could interfere and cause fast analog switching (instead of our "digital" full-off and full-on (even when "modulated" by the PWM which is "digital" but with varying on times. ] Then 2 stages. First the initial basic and "fall back" circuit without the PIC. Top of LED string (ie "top" = +ve LED end) to +12V. -ve Kathode end of LED string to the bright resistor (820R? 680R? with its other end to the added dim resistor AND MOSFET Drain else relay contacts (ie 30 or 87). MOSFET Source or other relay contact (ie 87 or 30) to GND (0V). The remaining (bottom) end of the added dimming resistor also to GND. With the FET off or with relay contacts open (ie, the relay is de-energised), the LED current flows thru the LEDs and both the bright and dim resistors and is hence DIM. The FET-ON or relay closed bypasses the dim resistor to GND, hence current thru LEDs thru the bright resistor then thru FET or contacts to ground, hence the LEDs are bright. IE - FET or relay turned on for BRIGHT LEDs. The 2nd & final stage is with the PIC providing bright/dim PWM and flashing control etc. Relay contacts are replaced with MOSFET (connected as above). MOSFET Gate (with say a 1M pull down resistor to GND) thru (1k?, 10k?) resistor to PIC PWM control signal output. Remove the dim resistor. [Pull at least one leg, or cut its wire for later fallback, or use a switch or (maybe - subject to corrosion and vibration) jumper or header pins (yeah - if current rating ok...) if you want easy swapping between PIC & "dumb" version.] Or you could leave the dim resistor in place, but then the LEDs will not extinguish unless the LED +12V (or GND) is removed. It will PWM etc between fully bright and taillight dim. Voltage regulator: Only one is needed to power the PIC itself. Inputs etc do not need "voltage regulation", but they usually cannot exceed the PIC's 0-5V. But 12V etc inputs can be scaled down using a voltage divider (whose output is proportional to input as the on the ratio of 2 resistor). For a car there might (should?) be some extra protection, but that can be added later (caps, maybe a resistor & zenor, or MOV (for spike protection). I'd suggest the common 7805 5V 1A regulator (in a TO-220 3 terminal package) for ~$2. The slightly cheaper and much smaller 100mA 78L05 could be used, but maybe the easier to handle and larger 1A version for the initial prototype.    (An adjustable & thermally self-protecting 317 can be also used by adding 2 resistors, but maybe KIS it now & use the preset 7805 5V regulator._ Both 780x & 317 regulators handle a max ~+35V supply depending on current and heat-sinking. The final thing is grounding, the PIC should be well grounded to the FET, but the FET to LED assembly;s GND should be separate and heavier, but that's probably thru the GND body/chassis anyway. The 7805/PIC +12V can be on the same circuit as the stop and tail-lights (are your lights or brakes on without IGN? Maybe then power the PIC from +12V, or diode feds from IGN +12V and brake-on +12V and tail +12V, so if any turn on, the PIC (boots up) & operates.

Good Morning!  These are my changes based on the above.

ajm

Pretty close... I've redrawn with some changes and notes. Some changes are merely "layout" - eg, the 1M MOSFET G-S resistor moved to emphasise it's between G & S to ensure the MOSFET remains OFF when no other Gate signal applied. Also a symbolic splitting of the GNDs since the LED & MOSFET grounds will be "heavy" for LED (or bulb) current while the PIC ground can be "light" (ie, 100mA max) and tied to the inputs. I also added another sting to confirm how the other strings are connected. I was also going to add the "stage 1" alternative for the FET - eg, the dim resistor with its paralleled 30 & 87 relay contacts DS FET connections. IE - the resistor and relay can be used as a backup in case the PIC fails (with some re-wiring, and then it's ONE dim resistor for ALL strings which means a smaller value ("dim-Ohms" divided by the number of strings) with a higher wattage. But there are different ways of doing that - eg, multiple "paralell" dim resistor as per that other link's circuit, or one big resistor as per my "series" circuit knowing that then "dim" will a bit brighter if any strings fail... Since this is stop & tail, only one output & FET circuit is needed. If it included left/right flashers, then a 2nd output and duplicated FET circuit would be needed.       You next theoretical step is to determine how the stops & tails are powered. IE - are they both via IGN, or both anytime, or tail anytime and stop only with IGN? Hence what +12V circuit supplies the light & brake switches that illuminate the lights? That will decide where you get your PIC power from, unless you want to change the standard wiring (eg, maybe brakes on anytime whereas they were originally only on with IGN. The other part is confirming that both tail & brakes are +12V switched, but that is the most common method. (Lights are almost always permanently grounded and +12V is switched to them to turn them on. However, especially with the advent of electronic management systems, it may be that their input circuits (switches) are ground signals and the electronics convert that to +12V (maybe via a relay).    But we can discuss the possibilities or best way once their power sources and switching are confirmed.    Then comes the "input" decisions. Since your stops & tails can be on independent of each other, you need to sense BOTH - ie, 2 inputs. But that doesn't mean using 2 PIC inputs. You can combine the 2 signals (through resistors) to get an analog output. EG - both off is 0V. Tail is 2V. Stop is 3V. Both means 4V etc. A single PIC analog input can then used to determine what is on. The latter is not an issue for you whereas with flashers included, it's another 2 inputs (left and right or both), hence another 2 PIC inputs or another one PIC input if we use a similar brake/tail combination trick. Of course, tails, stops, left & right flashers could be combined into a single PIC input, but that starts to get nightmarish! (Only in desperate situations might we do that - eg, if we are one input short). [ As you probably already see, there are so many ways that "inputs" may be available (ground or +12V), and then there are so many ways we can "sense" them (1, 2, 3 etc PIC inputs), so many ways they can be manipulated (PIC program to flash brakes, and maybe off the tails when the stop is flashing), and then alternative output or "drive" methods - eg, switch +12V to the LEDs using relay(s) and parallel resistors, or switch ground (or +12V) to series resistors, etc etc. Hence the multitude of solution for "the same problem" or design. Hence too why there is a stage where even I will ask "what have you got - and want" because the possible solutions take chapters to describe.   I prefer knowing the ins & outs and then restricting the conversation to limited solutions (eg, relay, PWM, PICs or other). ] Pardon the digression. I wanted to keep at least one PIC input as a possible speed sensor, or for anything you might want to add later. (Maybe music modulation at shows etc - when engine not running or car in motion (another PIC input?) The beauty with the PIC or any uPC type circuit is that once you have established basic input and output circuitry, it is simply a reprogramming of the uPC to change its behaviour (eg, dimness level, off or dim between brake flashes). There is no need to change or rewire and circuits! (Unless perhaps extra inputs are added, or extra output channels (left & right) etc. (Hence we try to leave spare inputs or outputs so we merely ADD the new stuff.) Now I might heed your "good morning" and have the coffee and breakfast I intended to have BEFORE I replied. (My pre "wake up" replies are infinitely sus!) Not that I'd be likely to forget to attach my redrawn circuit. (Read: Phew!)

Good afternoon! I can't begin to thank you enough!  Without you this project would have been pretty lame.

I am waiting on the picaxe chip and the resistors for all the LEDs. The only thing I have to figure out is the kind of N-Channel Mosfet I need.. I have everything else.. Oh.. I have to figure out the math for the voltage spitting on the restistors and go pick them up locally... hmmm whats left besides testing.. oh yah.. YOU ARE AWESOME.. Thank You THank You THank YOu.. I really appreciate you taking time out of your day to help me!!!

Ohhh.. and the idea to just flucuate the voltages and combine into one input is genius.  Kudos!!

I will be going over the PIC manual the next week while I wait for parts to come in

Off to bed.. I also noticed this blog has gotten quite the attention.. guess led stuff is pretty darn popular these days...

Good Night.. almost 10 PM here. 

ajm

Thank you Master for your compliments though your enjoyment & learning etc is probably the biggest buzz. This is the 2nd time someone has "jumped" at the PIC solution. I am somewhat cautious about suggesting them as people see them as too complex. Yet ultimately they are "THE" solution, and simpler and cheaper than most. (I am even adverse to some of the multi-relay circuits on this forum - though don't get me wrong, I highly admire their brilliance and that they solve complex issues using mere relays and novel wiring - but for some things I reckon the addition of a transistor (especially for delay circuits) or simple circuit is worthwhile. That's a bit more than using diodes, but IMO not much.) Yeah - I like the input-combination trick. That's something "common" I picked up either from my own brainstorming or from seeing old remote (corded) "switch to analog" circuits for transmission down a pair of wires rather than a common and one wire per switch.    Such knowledge and ideas accumulate with involvement. (Then comes my old age when they get forgotten - or maybe just temporarily misplaced or buried.) After a while I think many see things as I do - everything is the same, only different. By that I mean how you can translate a method from one discipline to another no mater how different the disciplines are. (Whilst water is commonly used as a model for electricity, I mean other things like where maybe a car gearbox solution is the key to solving a uPC or electrical problem. Not that a good example comes to mind at the moment....) As to the FET, as I see it, any N-type (aka N-ch or N-S) MOSFET (ie, power FET) with copious Amperage handling. Whilst you might only need a few Amps, I'm thinking of the many 60A to 120A MOSFETs I have bought for $2-$3 from markets or normal electronics chains. They are often the common TO-220 package (same as the bigger 1A or 1.5A 7805 etc voltage regulators). Why not (a 60A MOSFET etc)? All we care about is sufficient volts to turn it on (eg, Gate to be 4-5V higher than Source) since they are all low current (uA compared the the mA the PIC can supply). They have no "gain" per se - not like a transistor where you require (say) mA for its Base (Gate) and might then only get out 100mA or 1A so then you need another transistor to increase to multi-Amps. (Or make or get a "Darlington Pair" which is 2 transistors with a smaller driving a larger to give gains over 1,000 or 10,000 to get from mA to (say) 10A output.) And so what if your FET can handle 120A and you only need 20mA or 2A or 20A? Simply put, up to a 5 volt Vgs "fully on" rating, and more than (say) 2A or 10A output (Ids). (Vgs - the max V from G to S - is usually over 50V which is more than enough for our 12V (or 14.4V etc) circuit. See what's around that is N-channel; has no more than 4-5V Vgs for fully on (so the PC can control it); handles enough Amps (10A or more?); has suitable packaging (eg, 3 pins, TO-220 etc); and is CHEAP. A final check might be its Rds = Resistance between Drain & Source when (fully) on, but even if as high as 1 or 2 Ohms, it's insignificant compared to the 120R or 150R LED resistors. (120R in 10 parallel strings means effectively 120/10 = 12R which is stil reasonably higher than 1-2R. And MOSFETs usually have resistances of mill-R (milli-Ohms) - especially high-current MOSFETS.)    The only warning with FETs and MOSFETs - they can be damaged by static discharge, but most modern devices have static protection (ie, inbuilt spike-protection diodes). Otherwise (or anyhow) handle with care. Try not to touch the pins unless you are "grounded". [ Static electricity can be hundreds or thousands of Volts but at VERY low current, hence most components simply "short out" any static. But since FETs only require nA (ie, they have VERY high impedance/resistance between terminals), the static voltage may not be shorted out and may instead puncture the device - eg, 100V static breaking thru the 60V Vds rated D-S or breaking thru the Gate to D or S). ]      Mind you, back when CMOS was popular, the same warnings applied (and still do). However I never bothered about earth/ground wrist-straps tied to conductive surfaces. I'd leave them in tinfoil (pins thru tinfoil) or their conductive foam etc and handle the tinfoil or foam, and touch the destination circuit with my other hand before fitting the CMOS chip (or FET) to the circuit. IE - use your body/hands to equalise/connect all voltages in case static was present. I never had any problem - at least none that I know of.    Actually I'm not sure if the PIC has similar warnings, though I don't recall any. (It probably has static protection. Certain uPC chips may not. Are we allowed to "touch" the pins on Intel i5 chips etc?) For LEDs that require dimming, I have concluded that PICs are the answer. Unlike the old days when - for example - vehicle dome-lamps could be dimmed with a simple "analog" decay circuit, LEDs must be PWM'd (ie, voltage held constant but with a decaying -cum- chopped current). (As for new days & LEDs, I'm not even bothering with HIDs. IMO LEDs are not that far off. Well, they are here now, but I mean in my affordable way.) Even for a simple LED dimmer where a 555 with a handful of components can be used, a PIC only requires the 2 programming resistors and a similar pot (variable resistor) to set the brightness, but no timing caps or resistors or diodes. Sure, the PIC might need an output buffer (ie, "amplifier" for current gain - eg, a FET or transistor) but so to does the 555 if more than ~200mA. And the PIC needs a 5V regulator, but the 555 must have some protection from the higher spike voltages in cars etc, and it needs caps due to internal high-current switching (which can otherwise cause false triggering). And for power conservation, the 555 uses a minimum of 10mA (plus whatever output current). What's the PIC use - 7nA in standby? Not even 1uA when in operation? (I too must check its specs!). And with an 08 PIC being only a couple of dollars more than a 555... Yeah - PIC is the way. BTW - I called you "Master" because of your massive research etc. Also that you seem to have adopted the PIC within days. I've held off for a decade - or is that 2 decades now? [ Admittedly I stuck to uPCs for the big stuff I want(ed) to do. But now that the 08M2 has the same program space as its bigger family, it has greater application. Still though, I've know for years that a single PIC could do what multiple other chips and components cold do. Now wouldn't you think that an experienced ex-pert like me would have jumped sooner? Then again, not that I have necessarily built any of my intended projects. And noting "ex-pert" as in a "has been - drip". ]

Okay.. so here is my final diagram.. I am waiting on the rest of the parts from various parts of the country..

I went to the library and picked up "Teach Yourself Electricity and Electronics" which has been awesome..

Also learned that there is a difference between a diagram and a schematic.. hehe  Lot of good info in this book..

Trying to figure out how capacitor ratings work now... Might have to get another book for that.

Have a great day!

ajm