Total NOOB looking for help with motor direction.

[aquamon]

You can' drive 2N3055 with 39k

If that message is for me, the equivalent is NTE 85.
Dunno where you came up with such a physically large trans; AND, in the circuit given: 39K works just fine.
I had a 75K (R3) to start with that was also doing just fine.
BUILD IT; then, do verbally after.

 

[aquamon]

You can' drive 2N3055 with 39k

I agree, you can´t if it is the ONLY transistor...
In this case, it is NOT; so, you ¨CAN¨ ´!

 

[audioguru]

In the other thread, the motor current is only 35mA which is almost nothing. The base resistor of 39k ohms might have 10V across it causing a base current of almost 0.3mA then it might be able to have a collector-emitter current of only 35mA.

An NTE85 is a little low power transistor with a maximum current of 500mA. A Japanese 2SC945 has a maximum current rating of only 100mA. A TIP122 darlington power transistor has a maximum current rating of 8A. A 2N3055 power transistor has a maximum current rating of 15A. They are all different. Compare their datasheets to see the HUGE differences.

 

[aquamon]

In the other thread, the motor current is only 35mA which is almost nothing. The base resistor of 39k ohms might have 10V across it causing a base current of almost 0.3mA then it might be able to have a collector-emitter current of only 35mA.

An NTE85 is a little low power transistor with a maximum current of 500mA. A Japanese 2SC945 has a maximum current rating of only 100mA. A TIP122 darlington power transistor has a maximum current rating of 8A. A 2N3055 power transistor has a maximum current rating of 15A. They are all different. Compare their datasheets to see the HUGE differences.

Doesn't matter what size resistor used, use an SCR for all I care or just short the base/collector.
I tried with motor of up to 200mA already w/out changing a thing.
Even stalling the motor out to over 0.1A as stated on diagram.

Like I said before; this circuit is for others...

 

[audioguru]

You did not show your schematic with the actual transistor part numbers that you used and the actual currents and voltages that you measured.
A 12V motor might barely run when it is powered from only 7V.

We design circuits where a 12V motor gets close to 12V.

 

[aquamon]

You did not show your schematic with the actual transistor part numbers that you used and the actual currents and voltages that you measured.
A 12V motor might barely run when it is powered from only 7V.

We design circuits where a 12V motor gets close to 12V.

Why are you trolling?

If Ross1966 requires a circuit, i recommended this.
He can use the led input-to-base directly as a micro-switch instead with his mechanism.
This is where the ¨ḧelp¨ should be directed.

The motor I used was for testing purposes.
I later added 12V and the actual motor from the rc heli i gave link to.
without changing anything, it worked flawlessly.

The only drawback to the diagram is R2´s value; of which nobody has commented on.
For reverse, I´ll live with that.
Thank you.
See you next 4 more years from now; maybe not.
Goodbye trolls.

 

[Colin]

I put this circuit (from the forum) on my website and said it was a waste of power transistors.

The designer of this circuit immediately screamed at my provider that I had defamed him by saying:
"Here is a circuit using just NPN transistors. They are ALL Darlington transistors and this is a waste of expensive transistors"
If you read the replies he has received from this website you will see that others have already said that the circuit is quite unworkable.
In fact if you work out the voltage drops across the Darlington transistors you will see the motor gets 6v for a 12v supply. A 6v supply will provide almost NOTHING.
Not only that, but you don't need power transistors for loads around 100mA or so.
Just because a circuit works, does not mean it is a good design and in a previous design he used 2N3055 transistors with 39k base resistors. You don't use 2N3055 transistors for 100mA loads.

 

[JonSea]

Why bring this up 2 years after the original post?

 

[Colin]

"Why bring this up 2 years after the original post?"
Because the designer of the circuit only brought the claim of copyright infringement last week.
The fact that I did not mention his name and he claims: I made a defamatory statement to the owner.
The only sentence was: "Here is a circuit using just NPN transistors. They are ALL Darlington transistors and this is a waste of expensive transistors"
My service provider is not interested in the truth. They just get frightened that they will be sued.
In fact I am allowed to make technical corrections to a work and the circuit above is one of the worst designs I have seen.
The designer is obviously not interested in fixing the design and does not understand what he has been told by three other qualified engineers on this forum.
Luckily it has not been released into Google images as I am trying to clean up the web by exposing shoddy designs and showing readers how to design things correctly.