[img] https://adjuntos.yoreparo.com /imagen_post/0005/33/e9566d72560f6806ae6594a4cd08f24e8fcf5b4f.png[/img[ original internet photos I try to copy
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Electronics and Circuits
Can you guys help me with this homemade adjustable source and transist
62
hace 5 años
hace 5 años
good I made this same internet scheme only with other types of ponteciomes and resistance, 20k ........ I feed it with a 30v source to this scheme ..... it worked out well I regulate the voltage everything well but when I connect a motorcycle 12v bulb for testing and put the thermocouple function and proceed to see the temperature, the transistor mje 2955 gets too hot .... I put a heatsink and it warms up to such a degree that the finger cannot be left stuck. . more than 70 ° as in 15 20 seconds ......... proceeded to take out the transistor and measure and that transistor is not short ... which can be ?? I don't think it's normal for it to warm up too much and that I do not put another device that consumes more [img] https://adjuntos.yoreparo.com /imagen_post/0005/33/e9566d72560f6806ae6594a4cd08f24e8fcf5b4f.png[/img[ original internet photos I try to copy
[img] https://adjuntos.yoreparo.com /imagen_post/0005/33/e9566d72560f6806ae6594a4cd08f24e8fcf5b4f.png[/img[ original internet photos I try to copy
5.128
hace 5 años
The cause is that the transistor must discard almost 10W that it does not use at all, so it goes in heat. There are welders that melt tin with 20W, and if we cut it in half it is still very hot. The component can withstand a large heatsink but it is a waste of energy. With the data you gave below, the consumption is 500ma (this current will be the same before and after the transistor); what changes is the voltage that the transistor must reduce (31V to 12V), it must "eat" 19V, so the minimum energy absorbed by the transistor is 19V * 0.5A = 9.5W.
hace 5 años
hace 5 años
The transistor temperature depends on the following factors:
1 Amperage consumed.
2 Voltage between the collector and emitter terminals.
3 Heatsink size.
To your question if it is normal to warm up so much, I will tell you if it is normal.
The smaller the heatsink the hotter the transistor will be.
The more amps you consume the more it will heat up.
The higher the input voltage and the lower the output the more it will heat up.
This type of regulators (linear) are inefficient and not very suitable for high intensities.
For such use it is necessary to resort to switched regulators.
hace 5 años
What is the source voltage and how many watts does it put in focus? Upload a photo of the regulatory circuit you did.
62
hace 5 años
the voltage of the hp source that I use is 31v the watt of lfoco is not described in the spotlight ... I only know that it is a motorcycle and it is powered at 12v and the circuit made it identical to that of the photo that is mounted of inter..and already review everything and everything is in due course the only thing is that I am not riding on a pcb ..... the mje2955 is mounted on a heatsink twice the size of it ... now that I think You tell me that it depends on the voltage between collector and emitter ... I don't know if I have to see that my source is 31v that I regulate to 12v and in between the tutorial they put the source already in regulated 12v and those 12 v ...
hace 5 años
The photo heatsink is ridiculously small. For what you are doing.
31 volts of input minus 12 of output gives us 19 volts in the transistor that multiplied by the 3 amps of a motorcycle lamp gives us a total of 57 watts.
With that power dissipated you will tell me if it is normal for the transistor to be more than warm.
hace 5 años
As I see you are a Neophyte, I want to tell you something. You cannot alter the values of the schemas of a data sheet of a component.
By not setting the same potentiometer value you are changing the output current of the LM317 and that implies poor stability in the regulator when the load consumes little intensity. That integrated requires a minimum intensity to work well and that is done by the value of the potentiometer and the resistance of 240 ohms.
hace 5 años
Motorcycle lamps are at least 35 watts, that means that if it works at 12 volts it has to consume at least 2.9 amps.
hace 5 años
I want to tell you something else. Take it as advice from a veteran. Electronics is a multidisciplinary branch of physics and is composed of several branches of the exact sciences.
As all science is subject to premises.
Measurement of magnitudes, theoretical knowledge, mathematics, empirical verification.
If you really want to reach something in electronics, apply and comply with the canons.
The tips have two good things.
1st are free.
2nd You can take them or leave.
hace 5 años
I already told you that the heatsink has to be 5 times larger.
https://es.wikipedia.org/wiki/Ne%C3%B3fito
62
hace 5 años
I know you have to study but I don't think this page is only for veterans with knowledge ..... one that others will have more knowledge than others ... that's why this page is made to guide anyone who wants to do it and for their valuable response and knowledge and help will be rewarded by positive votes ...
hace 5 años
I repeat that it is advice. If you want you take it and if not nothing.
Depending on what you decide, the results will be for you.
I don't know what goals you have in this electronics.
The difference between starting as mandated by the canons or doing it in a compadre style is evident.
The one who does it well will be a remarkable electronic technician and the one who is not mediocre.
1.651
hace 5 años
Dear, let's not fall into polemic and stratum. Veronica, it is like that, in the forum there are many levels, and even the one who knows the most, always learns something. JOSE MIGUEL S, although I understand your reasons, and your advice is correct (I give my positive), we must be careful not to be hurtful or offensive. Let's leave it here. It seems to them?
62
hace 5 años
No, Mr. Jose is not offended and I do not feel offended at all, but this forum is for learning ... and even the most experienced or learn something in the least or if they are not here for what? If it is not to learn It is to explain and give his knowledge, and simply he who does not want to answer alone DOES NOT ANSWER ... he recommended me to study ... I did not look for that answer ... as well as I qualified negative ... he does not know where I live or the situation in which one is .... to know if I can study LA RAMA MULTI BLA BLA BLA
hace 5 años
I have answered what you asked by giving you the solution to your problem and list the reasons why transistor warming occurs.
You have to put a heatsink 5 times larger on the surface.
I terminate the query you made.
hace 5 años
Thank you for the recognition heating MI. If I have allowed myself the license to give those advices, it is because from experience it is difficult to earn the wage with this profession.
By advising Veronica to study, it does not mean that she is saying that it has to be for work to get a university degree.
When I started on this there were no facilities and means there are today and everything was much more expensive.
In case it is worth something I will say that I have no degree other than compulsory education and I have studied self-taught combining work and study.
23.097
hace 5 años
I congratulate you José Miguel, since you have acquired solid knowledge of the scientific bases, if you do not mention it you would not notice that you have not completed technical education, since the logic you use applies to any specialty: magnitudes, calculations, tests, verification and results. When I grew up I had to learn electronics to be able to continue in the market of my trade, already 7 years ago, and at 50 and I can say that it is never too late to learn, and if what you learn helps you to earn a living, it is a lot best. Greetings and congratulations!
hace 5 años
Dear Calefaccion MI, I acquired my knowledge in a long process of ceaseless study, combining it with hard work. My father died a long time ago and left my mother a widow running out of economic resources of any kind. I was the oldest of three brothers and I found myself in the duty of maintaining the family economy by working in two jobs and studying on my own.
He who does not learn is because he has no will (Vague). I trained myself studying philosophy, theology, parapsychology, hydraulics, pneumatics, electromechanics, physics, chemistry, electronics, Italian
hace 5 años
I am currently studying Japanese when I have free time and I continue to progress in electronic engineering issues designing custom electronic circuits to solve specific problems.
I take this opportunity to tell you that if you have a problem related to electronic circuitry, you can count on my help.
I have different circuits of my invention that I designed for problems that arose.
The latter is a switched regulator for motorcycles that has an efficiency greater than 99%.
hace 5 años
The key to learning consists only of perseverance and learning from other people who know more than one.
It is difficult to come to fruition by giving blind sticks and despising those who reached and mastery.
It doesn't matter what it takes to reach the goal. The important thing is to learn along a defined path.
Know where you are, where you want to go and how to make that path.
Before running, you need to learn to walk well.
1.651
hace 5 años
hace 5 años
I add fact sheet that supports what JOSE MIGUEL S said
mje2955.pdf [126.91kb]
Greetings from Uruguay
mje2955.pdf [126.91kb]
Greetings from Uruguay
1.096
hace 5 años
hace 5 años
Hi, you have 3 ways to improve your font;
The first is to replace the heatsink with a larger one.
use another source of lower voltage, in your case with 15 v would be fine.
The last one is to use your switched source directly, modifying the internal circuitry, you have some cons, being of a considerable value 30v, if it is reduced a lot it can reach its minimum point, which could not serve or damage the integrated switching.
regards.
62
hace 5 años
Thank you ....... and seen by inter that they put a dsrlintong transistor as a step transistor and thus have more amperage and do not damage the lm317 ..... it will be that he removed that 30v source and set it to 12 I have a disposable power source ... and could I use it to Max 5 I love 12v what do you think? Will it be that 12 v 5 master will help me to try things? How much could I use more than 12v?
1.096
hace 5 años
Hello, if I could put a Darlington but it will still get hot, because ?, In circuits there is one of many laws and theorems, in this case it is the Kirchhoff voltages law, this law says that the sum of all voltages must be equal to zero, so if there is 12 V at your output and your source is 31v, then the voltage drop in the collector to emitter transistor is 19v and if the current is considerable then the heating is due there
1.096
hace 5 años
If you like, you can use this circuit, in the document I analyzed it for a colleague to understand how it worked. Https://drive.google.com/file/d/1gbpDeRZMQSzhWOdLrjrBBzeZDp2iZvd8/view? Usp = drivesdk. Greetings, I hope and serve you.
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