Electronics > Beginners

Need trouble shooting help (pics)

<< < (6/9) > >>

alsetalokin4017:

--- Quote from: billbyrd1945 on February 23, 2019, 05:16:07 pm ---"I see the current in question as ".056Ma" when it should have been .056A. The difference between Ma and Amps. 56Ma would have been correct. I knew what you meant."

Ah! I see what you mean. I used the wrong label.

--- End quote ---

Ah..... no.

Ma is not a usual electronics abbreviation. The capital "M" usually would indicate MEGA, that is, MILLIONs of amperes.

The correct abbreviation for "milliAmps" is mA. Not Ma.

So in your original post where you stated the current, you either misplaced a decimal and/or used the wrong abbreviation. I even quoted and bolded your text, up above, so you could see where you made your error. 

Believe it or not, these little nitpicking things are important, and it does a beginner a real disservice for someone else to "know what you meant" instead of pointing out the error so it doesn't get made again.


As far as reading and interpreting data sheets for transistors... usually on the first page on top you may find the most critical information you really need: the pinout,  the maximum collector-emitter voltage, and the maximum rated collector current. And the usual application information may help you select the proper transistor for your application. A "saturated switch" BJT would be better than an audio amplifier for turning on your motor. And of course a mosfet would suit the actual application better but would teach little about the use of a BJT.



billbyrd1945:
"I goofed by not giving enough information. The video was https://www.youtube.com/watch?v=8DMZSxS-xVc. And I used the same transistor (PN2222A). The motor I have just happens to draw .056mA"

As far as I can tell, the only time I mentioned a current capacity was small m, large A. But it should've been amps rather than mA as Arthur pointed out. And don't think I don't appreciate your eye for detail. I retired from a medical career where such errors could kill. As to the datasheets, I can read what they say, just not yet sure what it means. But I'll get there. Do you think that the "audio" feature would have any bearing on the pulsations?

ArthurDent:
In the video I don't see the 4.7K current limiting resistor in series with the +5 VDC and the transistor base. Not having the resistor in the circuit could be very bad for the transistor.

alsetalokin4017:
One other thing that should be pointed out is this: That little motor when given 12 volts, unloaded and running freely, draws about 54 or 56 mA, well within the max collector current of the small transistors, as you've shown. But at initial startup it will draw more, maybe a lot more, maybe enough to blow or stress the little transistors. Ditto if the motor is heavily loaded or stalled. The initial startup surge will be over quickly once the motor is running at speed so the transistors may survive even if the peak current is over their "absolute max" rating.

The surging you see in your video could be caused by a number of things but my first guess would be the power supply sagging. I'd also change the transistor just on spec.


You will find either mosfets, or BJTs inside the typical compact fluorescent bulb. I've seen both, and same brand bulbs may use either circuit. You can experiment with either type in this present motor circuit.  You will usually find at least 4 diodes of the 1n400x variety or equivalent, the two transistors, a big electrolytic cap and some smaller film caps. I usually don't bother with the resistors or inductors in the CFL circuit but they too can be scavenged if you really need them for something. Be careful not to break the glass, there is a tiny amount of mercury inside.

alsetalokin4017:

--- Quote from: billbyrd1945 on February 23, 2019, 07:55:57 pm ---"I goofed by not giving enough information. The video was https://www.youtube.com/watch?v=8DMZSxS-xVc. And I used the same transistor (PN2222A). The motor I have just happens to draw .056mA"

As far as I can tell, the only time I mentioned a current capacity was small m, large A. But it should've been amps rather than mA as Arthur pointed out.

--- End quote ---
Or you could have moved the decimal three places to the right and said "56 mA" which would have been completely correct.

--- Quote ---And don't think I don't appreciate your eye for detail. I retired from a medical career where such errors could kill. As to the datasheets, I can read what they say, just not yet sure what it means. But I'll get there. Do you think that the "audio" feature would have any bearing on the pulsations?

--- End quote ---

No, it just means the transistor is optimised for rapid oscillation (audio) and varying signal amplitude. A 'saturated switch' type is designed to be fully on or fully off, and wastes slightly less power.

I'm looking into the pulsations now.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod