boylesg
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The formulas near the schematic have several typos (e.g. + Q1 in the last line should be + ßQ1). Ireq means probably Ireg.
R1 of 3 ohm means that the power transistor starts to conduct at Io of about 0.2 A and keeps Ireg constant around 0.2 to 0.25 A for higher Io.
Start with Vbe,Q1 of 0.6V.
0.6 V/3 ohm = 0.2 Ampsstiill don't get any where near 0.2A
FvM wanted to say Veb.Start with Vbe,Q1 of 0.6V.
Hi,
Ireq is the required current through the regulator, IQ1 is the current desired to pass through the pass transistor.
Without knowing the datasheet current expectations, let's suppose about 2A, with stated 0.2A for regulator and say Beta of 100...
R1 = 0.6V/(0.2A - (2A/100))
R1 = 0.6V/(0.2A - 0.02)
R1 = 0.6V/0.18
R1 = 3.333 Ohms.
I give up on the second formula as I get nothing sensible, no matter how I calculate it...
Who cares, the main one is the first one, to know how much you want to pass through the regulator, and how much through the transistor. I believe with this circuit it is good to know the maximum current that will be needed, as the pass transistor:regulator current is a ratio, not a limit.
Hi,
It took me ages to understand that formula (because I'm not gifted with these things), also asking on a forum, and besides that, this was the only other explanation I found at the time: Understanding 78XX high current voltage regulator
If you ever have to get round to the bypass and short-circuit transistor version (figure 14), that is also easy to understand (takes a bit of trial and error to implement satisfactorily) once you get your head around it.
After having another go at formula 2...
Io = 0.2A + (100 * (0.2 - (0.6/3.333)))
Io = 0.2A + (100 * (0.2 - 0.18))
Io = 0.2A + (100 * 0.02)
Io = 0.2A + 2 (A)
Io = 2.2A
...phew, formula 1 and formula 2 give the same result! (give or take a few mA if done with a calculator)
I agree with your point about manual writing, but this happens with everything - software manuals or planting peppermint seeds to DIY furniture manuals, steps are skipped a beginner/newbie will not know, but nor is it the writer's fault - they can't be clairvoyant and have to assume a mimimum of knowledge in a given area. What's "bad" is when the basic formula includes somewhat more complicated terms in them that need to be discovered then calculated first and you can't proceed before doing so
If this is also for the Tesla thing circuit, it would be great to see it finished when you get there, looks interesting.
Especially many Asians who also can't write good English on top of not being able to write a good manual! Very frustrating at times.I agree with your point about manual writing, but this happens with everything - software manuals or planting peppermint seeds to DIY furniture manuals, steps are skipped a beginner/newbie will not know, but nor is it the writer's fault - they can't be clairvoyant and have to assume a minimum of knowledge in a given area. What's "bad" is when the basic formula includes somewhat more complicated terms in them that need to be discovered then calculated first and you can't proceed before doing so
No technical people are often terrible at writing manuals, there used to be technical authors who could do the job properly but as with everything cut backs etc. mean that they expect engineers to do everything and it does not work, technical authoring, PCB layout and CAD library management are three main areas where the correctly trained people should be doing the job, not engineers doing it as a part time supplement to their primary role.
Great, thanks for sharing it, that's been fun to watch.Here is a video of a discharge I got from it
I found this excellent high current linear voltage regulator circuit:
Never mind....I read this: https://electronics.stackexchange.com/questions/77045/transistors-in-parallelIf all have base current flowing into them then how is it that one won't conduct?
[h=4]How to Calculate the Emitter Current Limiting Resistor[/h]
It is actually very simple, and could be calculated using Ohm's Law:
R = V/I,
Where V is the supply voltage used in the circuit, and "I" could be 70% of the transistor's maximum current handling capacity.
For example let's say if you used 2N3055 for the BJT, since the max current handling capacity of the device is around 15 amps, 70% of this would be around 10.5V.
Therefore, assuming the V= 12V, then
R = 12/10.5 = 1.14 Ohmshttps://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/
Never mind....I read this:["https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/"]
I put the value at 6.8 -> 8.2 ohms for a 3A max transistor. Does that sound about right before I go and solder them in?Right. You just need to lift the emitter leg by about 0.3-0.5V.
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