Constant Current Led Driver

Too many things to mention at one go....snip the bjt base wire and re-connect it through an Amp meter.... then ask yourself what action is the bjt performing.

Thanks for the reply. According to the designer the BJT is used as an over-current sensing switch, and R3 is the "sense resistor" or "set resistor" that triggers the BJT when too much current is flowing.

I suggested that you look at your Amp meter so that you would see that there is zero amps passing through to your bjt base at all times...in other words, on your schematic here, that bjt may as well be removed....it is not doing anything at all with no current ever at the base.... see  http://everycircuit.com/circuit/5340424565948416

This is exactly why I wanted to accomplish a working model before I actually build the thing. Thanks for the info.

With the EC schematic of mine on the left there, I recognised what was needed to make it work, then I made the necessary adjustments in the Nmos settings. In reality however, those settings can not be adjusted, so it is necessary to alter other components to achieve the same goal... but you still need to know what that goal is for the Nmos action.  If we simply require a full on/off switch action from the Nmos, then it is easily achieved with little more thought other than attaching the Nmos Source directly to earth and being aware of the amount of current flow. (and ensuring that the gate V passes the Vth to switch it on). With any other Nmos setup however, more Nmos knowledge is required to get its individual settings structured to perform as we wish. Simply following a seen schematic instead is not always likely to work. Every individual Mosfet has different settings such as its Kn value, and that needs to be ascertained and accounted for, otherwise a component (such as itself) may blow or just not work, as you have found. See here for more about a Nmos http://everycircuit.com/circuit/5338883035496448

Waste heat power at the mosfet may be your biggest problem in this setup where the saturation region is used with a large volt drop across the mosfet and a relatively high current flowing. More LEDs in line would lower that Mosfet volt drop.

Amused

 @btntx ... Interesting alterations which you are trying there now.... keep an eye on realistic current throughout the bjt.... and is that 12v supply facing up to the logic train really needed....If you snip that 12v to the resistor, then you could also reduce that resistor value and get rid of the zener. Then with an alteration of the Mosfet settings and its source resistor you would arrive at the web that you are working through...step 8 #5 That would keep the current constant just as before, but with a realistic μA level at the bjt base with less than 20mA through the collector. Something along these lines at that stage http://everycircuit.com/circuit/4626404506599424

This is the theoretical red channel of 2 common anode rgb leds. I was able to fudge around and get the current that I want. I’ve learned a little but still pretty clueless. Thanks for the additional information. Will have a look at it later today.

Now with logic train the regulation is conpletely out of order. Check this and have fun with @2cent http://everycircuit.com/circuit/5482667675222016

Yours is not adjusted to work without the bjt Hurz. Mine here is .... but the point I made in the previous link was that it only applies to EC alterations ...read it there after viewing a working EC example here... http://everycircuit.com/circuit/6505624866390016

Here is a different approach while we are having fun here ... current mirror http://everycircuit.com/circuit/5120177569267712

@2ctiby you are a pain in the ass. You talked about " blablabla be careful about the BJT current...." bullshit. The complete BJT is in this case nonsense, because the logic train is not a open collector. Please look up whats the advantage of an.open collector, and think about how the logic train clamps the voltage to 5 or 0V doesn't matter whats connected to it. This voltage overrules the BJT action. Dont you see that? Ohh, boy.

Current mirror in 1:1 configuration, how funny you are. You waste two times of energy. Fun for 2cent.

Lets start with a mosfet free version, which keeps 2cent away http://everycircuit.com/circuit/5032061315579904

If you had read the notes on my earlier link you would have seen that I pointed the OP to a relevant web where the point was clearly made there about the current mirror using twice the energy. As for the bjt....the shown current in both the base and collector of the presentation by the OP there is too high for most bought bjt ...hence my comment to him. All of this is not my design project.... I have simply been putting forward Mosfet alterations experience for the OP. Furthermore, the OP wanted to use a Mosfet as described by his web viewing...he was not asking for your bjt-only effort which we can all easily find on the web.You are filled with your usual unnecessary hatred.

And all that hatred coming from the leader of the Troll hunters...!!!

The logic train was the start. At that moment @2cent was talking about current and BJT blablabla. As I just demonstrated in my equivalent circuit the logic train makes the BJT useless. But its always the same, Mr 2cent messes up foreign circuits and the end is a complete mess of.circuit like the "schmitt trigger" disaster. Tedski troll himself, zero circuits, changed his user account. Just here with the hope to meet big_p_joe. Shame on you both.

There speaks Hurz who has never been seen to do, or even discuss, mosfet settings/regions on EC, whilst professing ultra knowledge in all things whilst spitting venom at anyone who dares to question him, or who shows knowledge in any area which makes him feel threatened about losing ultimate dictatorship.... He is a deluded dickhead and EC would be better off without him so that all the guys could feel at ease making friendly (even if wrong) input.

One of my biggest hurtles is finding parameters for MOSFETs and BJTs. EC appears to be asking for SPICE parameters — which are not on Fairchild data sheets. How do you deal with this?

Teacher 2cent with the revolver at the students head and this glint in his eyes while he said, "today we all have FUN with my circuits".

Right - that’s it! The two of you go to your rooms until you can play nice! You guys must be engineers. :)

Hurz, you really are some piece of work, for someone so knowledgeable about electronics, you lack in every other aspect, especially people skill, you are an idiot wrapped in a moron, now just grow up, and use your skill to help others...!

@btntx ... It's good that you are interested in finding more detail about Nmos parameters e.g. from a datasheet. My Nmos learning series which I pointed you to earlier mentions that. Using a mosfet without understanding those details is very restrictive. I strongly advise you to read through that series very carefully. If you have any specific question about a Nmos datasheet value etc. I will try to answer it if I can. Here is part 4 of that series for a quick glance http://everycircuit.com/circuit/4863487332581376 then at least glance at part 5 there too.

@2ctiby ... Will do. All of your assistance is much appreciated.

@Tedski, you are a troll and you are not here for electronic. Otherwise you would notice whats wrong with the logic train. But you dont care cuz you do not understand at all. Trolls like you are not welcome. Zero circuits and waiting for big_p_joe. What a poor individium your are. Last chance for you to explain what you do not understand or shutup.

@Hurz ... You still haven't learned to discuss amicably, instead you respond with contempt, anger and bitterness to many people's efforts...it will not work, because it only brings a poor response. Your point about the logic train overiding the bjt should have been presented much better. You seem to have missed the part just before that where I queried the use of the bjt being there at all, and then I went on to present a schematic without it. The Mosfet needed re-adjusting then because the bjt seemed to be acting more like a pull down resistor while it was there (clamped volts, yes... but current was passing through all the same... remember, the bjt base was attached to a non-ohmic actioned mosfet where standard V=IR does not occur)...which I had accounted for by the earlier Mosfet adjustments. I am quite happy to discuss such matters, but I will not continue with pointless insults.

All aggression are coming from you and Tedski. Long lasting comments without a single word of electronic. Typical.

Hurz, l paid my fee for this app, l am under no obligation to publish anything, l look at others work to try and learn from them, we are not all experts such as yourself, you can call me a troll if you like, thats what free speech is all about, and l am entitled to let you know that you are a big headed conceited ill mannered nasty person, this is my last word on the matter, because l know you feel you are so superior that you will keep this going for ever...!!!!!

Exactly, you know already everything so no need to talk about electronic. You even know what I feel. This is troll style. The community gave you a negative feedback shouldn't be an assignment to attack me. Its not my fault your ideas are not welcome. Listen to the community and argue with users of this community might change anything. But just sitting there and waiting for.big_p_joe is troll behaviour.

But the bad thing for you is, that everything said about you (Hurz) under this circuit is absolutely correct.