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Author Topic: 2n3055 transistor question  (Read 10144 times)

Offline TheOne

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2n3055 transistor question
« on: July 19, 2015, 05:02:12 PM »
From the picture attached, my transistor work, but I would like instead connect it like the right section (of the image) but it does not work.


Can I do it like the right section?


Because I want to put 2 transistors on the same heat sink, I want to put the 35V on the collector on both transistors (direct on heat sink) but
just want the other part with coil separated from each others, I don't have 2n3055 termal insulator and put the 35v on each transistor and without touching the heatsink...


Anyway any suggestion/help would be appreciated!

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2n3055 transistor question
« on: July 19, 2015, 05:02:12 PM »

Offline MarkE

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Re: 2n3055 transistor question
« Reply #1 on: July 19, 2015, 06:21:12 PM »
Your circuit presents three problems:

1) The emitter cannot rise any higher than 1 Vbe below the base.  Consequently the transistor dissipation will at least double from a low-side configuration and your heat sink sharing will be self-defeating.
2) In order to turn the transistor on, you will have to pull up to the 35V rail.  This means you will have to add a predriver stage.
3) The predriver will inject extra current into the load.

There are several alternatives that make more sense:

Use an N channel MOSFET in a low-side switch configuration that has a low enough on resistance that you can use a small heat sink or no heat sink at all.  How many amperes does your load draw?  This MOSFET is under $1. each from Digikey.  It's on resistance is nominally 12.5mOhms.  Even at 4A the power dissipation will be about 200mW.  No heat sink is needed. NTP5864NG  http://www.digikey.com/product-detail/en/NTP5864NG/NTP5864NGOS-ND/2748420  If you need a logic level gate then this is a few cents more and will dissipate about 300mW.  It is also fully insulated.     AOT2618L http://www.digikey.com/product-detail/en/AOT2618L/785-1438-5-ND/3603378

Use an integrated high or low side switch again with a low enough on resistance as to obviate the need ofr any shared heat sink.

Oh, and by the way:  Connect the catch diode around the inductor:  cathode to the 35V, anode to the switched side.

And you could always just buy one of these kits from SparkFun:  https://www.sparkfun.com/products/10618

Offline TheOne

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Re: 2n3055 transistor question
« Reply #2 on: July 19, 2015, 06:50:30 PM »
Your circuit presents three problems:

1) The emitter cannot rise any higher than 1 Vbe below the base.  Consequently the transistor dissipation will at least double from a low-side configuration and your heat sink sharing will be self-defeating.
2) In order to turn the transistor on, you will have to pull up to the 35V rail.  This means you will have to add a predriver stage.
3) The predriver will inject extra current into the load.

There are several alternatives that make more sense:

Use an N channel MOSFET in a low-side switch configuration that has a low enough on resistance that you can use a small heat sink or no heat sink at all.  How many amperes does your load draw?  This MOSFET is under $1. each from Digikey.  It's on resistance is nominally 12.5mOhms.  Even at 4A the power dissipation will be about 200mW.  No heat sink is needed. NTP5864NG  http://www.digikey.com/product-detail/en/NTP5864NG/NTP5864NGOS-ND/2748420  If you need a logic level gate then this is a few cents more and will dissipate about 300mW.  It is also fully insulated.     AOT2618L http://www.digikey.com/product-detail/en/AOT2618L/785-1438-5-ND/3603378

Use an integrated high or low side switch again with a low enough on resistance as to obviate the need ofr any shared heat sink.

Oh, and by the way:  Connect the catch diode around the inductor:  cathode to the 35V, anode to the switched side.


thank for your reply!


More explanation: actually I test with 5v + led and resistor, the coil stuffs is not done yet, but I have the problem with the LED so I guess the coil version would not work :)


I don't need a lot of amp since it is used for MEG input coil, I want higher voltage and low amp and all my circuit is powered by a raspberry pi2 GPIO 5v.


But about this transistor, I dont want to buy mofset and wait 2-3 weeks to continue to work on my circuit.


Can I use my transistor, if yes, they need to be insulated from the heat sink and each collector are managed like this new circuit diagram? I dont quite understand your pre-driver  stage :)






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Re: 2n3055 transistor question
« Reply #2 on: July 19, 2015, 06:50:30 PM »
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Offline Void

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Re: 2n3055 transistor question
« Reply #3 on: July 19, 2015, 06:52:25 PM »
From the picture attached, my transistor work, but I would like instead connect it like the right section (of the image) but it does not work.
Can I do it like the right section?
Because I want to put 2 transistors on the same heat sink, I want to put the 35V on the collector on both transistors (direct on heat sink) but
just want the other part with coil separated from each others, I don't have 2n3055 termal insulator and put the 35v on each transistor and without touching the heatsink...
Anyway any suggestion/help would be appreciated!

You are basically asking if you can use an NPN transistor as a high side switch.
Normally a PNP transistor is used in a high side switch configuration when using bipolar transistors.
However, even if you were to use a PNP transistor such as a MJ2955 instead of the NPN 2N3055,
you would stil have the same heatsink problem, as the emitter of the PNP transistor goes to V+ when
it is used as a high side switch. See the attached diagram.
Maybe someone who is very familiar with these sort of switching arrangements can offer a better solution
while still using your 2N3055 transistors, but it looks like you may well have to go with two separate 
electrically isolated heat sinks, or order some thermal heat sink insulators for the transistors if you can find some.
All the best...


Offline TinselKoala

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Re: 2n3055 transistor question
« Reply #4 on: July 19, 2015, 06:54:41 PM »
But Mark... the 2n3055 is a "magic" transistor. If you get a genuine one (as opposed to the fake Chinese ones with tiny dies inside probably from a 2n2222) they can do wonderful things that seem to be way beyond their published specs. Perhaps the OP wants to see these miraculous effects, and perhaps his aesthetic sense requires that they be on the common heatsink. I have a JT sitting here on my desk that uses a 2n3055 and lights up a NE-2 from a "dead" AA battery. (Of course it works with a 13003 and some other types also.)

It's too bad he's not my neighbor, I just checked my stash and I have more TO-3 mica insulators and mounting kits than I'll ever use in my lifetime.

http://www.ebay.com/itm/4-sets-TO-3-Transistor-Mounting-Hardware-Kits-Mica-Insulator-Screws-Bushings-/251202298797




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Re: 2n3055 transistor question
« Reply #4 on: July 19, 2015, 06:54:41 PM »
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Offline Void

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Re: 2n3055 transistor question
« Reply #5 on: July 19, 2015, 07:03:03 PM »
But Mark... the 2n3055 is a "magic" transistor. If you get a genuine one (as opposed to the fake Chinese ones with tiny dies inside probably from a 2n2222) they can do wonderful things that seem to be way beyond their published specs. Perhaps the OP wants to see these miraculous effects, and perhaps his aesthetic sense requires that they be on the common heatsink.

That was completely uncalled for TK. The guy just asked a simple question.
Ignorant condescending and insulting comments such as you made here are of no help whatsoever.


Offline MarkE

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Re: 2n3055 transistor question
« Reply #6 on: July 19, 2015, 07:06:20 PM »

thank for your reply!


More explanation: actually I test with 5v + led and resistor, the coil stuffs is not done yet, but I have the problem with the LED so I guess the coil version would not work :)


I don't need a lot of amp since it is used for MEG input coil, I want higher voltage and low amp and all my circuit is powered by a raspberry pi2 GPIO 5v.


But about this transistor, I dont want to buy mofset and wait 2-3 weeks to continue to work on my circuit.


Can I use my transistor, if yes, they need to be insulated from the heat sink and each collector are managed like this new circuit diagram? I dont quite understand your pre-driver  stage :)
If you don't need to support fast switching or significant current then you don't need a heat sink.

Parts from Digikey or Mouser can be had the next day.  If you want cheap shipping and you are in the USA, USPS priority mail shipping is usually about $7. and will typically arrive in 2 business days.

The diode needs to go across the inductor:  cathode to the +side of the coil when driven, and anode to the - side.  UF2001 diodes are cheap as are a bunch of other available diodes.  Even a modest sized coil can kill a beefy transistor if the inductive kickback is not clamped.

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Re: 2n3055 transistor question
« Reply #6 on: July 19, 2015, 07:06:20 PM »
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Offline TheOne

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Re: 2n3055 transistor question
« Reply #7 on: July 19, 2015, 07:08:52 PM »
It's too bad he's not my neighbor, I just checked my stash and I have more TO-3 mica insulators and mounting kits than I'll ever use in my lifetime.

http://www.ebay.com/itm/4-sets-TO-3-Transistor-Mounting-Hardware-Kits-Mica-Insulator-Screws-Bushings-/251202298797


I was watching this yestruday (http://www.ebay.ca/itm/TO-3-Mica-Insulator-50-x-Mica-sheet-100x-Nylon-bushing-2N3055-3773-Free-Shipping-/161541288294?pt=LH_DefaultDomain_0&hash=item259c9c7166)


I guess I need to buy some to continue my experiment :(


so If I use them I should not have any issue with my transistors.


I want to use this transistors because I have a lot of them and need to be used on a project :)




Offline MarkE

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Re: 2n3055 transistor question
« Reply #8 on: July 19, 2015, 07:09:57 PM »
That was completely uncalled for TK. The guy just asked a simple question.
Ignorant condescending and insulting comments such as you made here are of no help whatsoever.
2N3055's were once a big work horse.  These days there are for most all applications better choices.  I think that the SparkFun board is a good choice.  He would get multiple channels so if he blows up one, he can just use another.They use decent MOSFETs and it fits an Arduino (not Rasberry Pi).  I am sure there is something similar for RPs around.

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Re: 2n3055 transistor question
« Reply #8 on: July 19, 2015, 07:09:57 PM »
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Offline TinselKoala

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Re: 2n3055 transistor question
« Reply #9 on: July 19, 2015, 07:10:26 PM »
That was completely uncalled for TK. The guy just asked a simple question.
Ignorant condescending and insulting comments such as you made here are of no help whatsoever.

On the contrary, I am perfectly serious and I am, as you see, encouraging the OP to use that transistor. Can you deny that many people use the 2n3055 in various projects, and that it will work when other similarly-rated transistors won't?

Here's my own current favorite "magic" 2n3055 project:
http://www.youtube.com/watch?v=OgndINJHnd0

Offline TinselKoala

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Re: 2n3055 transistor question
« Reply #10 on: July 19, 2015, 07:14:09 PM »

I was watching this yestruday (http://www.ebay.ca/itm/TO-3-Mica-Insulator-50-x-Mica-sheet-100x-Nylon-bushing-2N3055-3773-Free-Shipping-/161541288294?pt=LH_DefaultDomain_0&hash=item259c9c7166)


I guess I need to buy some to continue my experiment :(


so If I use them I should not have any issue with my transistors.


I want to use this transistors because I have a lot of them and need to be used on a project :)

Actually you still will face the base drive issue if you are trying to drive directly from your microcontroller and are looking for hard switching. You can put a simple inverting driver stage using 2n2222 or the like, between the mcu and the power transistor, and then invert the signal in the code so you still get the right cycles at the 3055 output.

Could you please edit your photo so that it isn't so big? If you keep photos to less than 1024 pixels wide, it won't screw up the page width and make comments hard to read.

p.s. you could also just cut the heasink in half down the middle with a hacksaw....

Free Energy | searching for free energy and discussing free energy

Re: 2n3055 transistor question
« Reply #10 on: July 19, 2015, 07:14:09 PM »
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Offline TheOne

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Re: 2n3055 transistor question
« Reply #11 on: July 19, 2015, 07:14:25 PM »
on my raspberry pi2 I made a c++ program that control the PWM1&2, they can be switched from 1hz to +1Mhz and the duty cycle can be changed from 1% to 50%, it is why I want to use a heat sink, I don't know what is the max frequency a magnetite core can handle, I will need to experiment.

Offline TheOne

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Re: 2n3055 transistor question
« Reply #12 on: July 19, 2015, 07:30:42 PM »
Actually you still will face the base drive issue if you are trying to drive directly from your microcontroller and are looking for hard switching. You can put a simple inverting driver stage using 2n2222 or the like, between the mcu and the power transistor, and then invert the signal in the code so you still get the right cycles at the 3055 output.

Could you please edit your photo so that it isn't so big? If you keep photos to less than 1024 pixels wide, it won't screw up the page width and make comments hard to read.

p.s. you could also just cut the heasink in half down the middle with a hacksaw....


yeah that another solution, not sure if i will do that, sorry my phone take enormous photo and i did not scale down, next time i will use gimp to scale it down :)


My PI2 handle 2 PWM


PWM1 is using the defined frequency
PWM2 use the PWM1 * 2, then I use 2 NOR gate to make it ON at the right time


Offline MarkE

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Re: 2n3055 transistor question
« Reply #13 on: July 19, 2015, 07:38:51 PM »
What frequency do you want to drive at, and what turn on and turn off time is acceptable to you?

Offline TheOne

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Re: 2n3055 transistor question
« Reply #14 on: July 19, 2015, 07:44:59 PM »
What frequency do you want to drive at, and what turn on and turn off time is acceptable to you?


Any frequency really, from 1hz to 1mhz and same from duty cycle, right now I am using 10% duty cycle and 4 hz for led (test)
but I can change the frequency and duty cycle in realtime... I can post the program if some want to experiment with it.


Basically I think for a MEG, a low duty cycle is best with a higher frequency, but I dont know what a magnetite core can handle :)


Once all my circuit will be resolved, I will need to print a 3d core in PLA and i will fill it with magnetite without any glue

 

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