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Topic: another transistor quesiton (Read 3136 times) previous topic - next topic

robkiller

#15
Feb 12, 2017, 05:22 pm Last Edit: Feb 12, 2017, 07:54 pm by robkiller
Sorry my last post was no good trying to explain what i did.  This should be a little better.

Wawa

Where is the back EMF diode?
Leo..

larryd

No technical PMs.
The last thing you did is where you should start looking.

robkiller

Maybe not having the diode is my issue lol  Where would that go?

Wawa

#19
Feb 13, 2017, 12:01 am Last Edit: Feb 13, 2017, 12:03 am by Wawa
The diode (e.g. 1N4004) goes across the motor.
Cathode (ring) to +12volt, and anode to the collector.
The diode kills back-emf from a motor/solenoid when the transistor turns off.
The spike (without diode) could be hundreds of volts and could kill the transistor.

I assume you have connected 12volt negative to the emitter.
And Arduino ground also to the emitter.
Leo..

robkiller

Is this better?

And yes both 5v and 12v grounds are connected



allanhurst

do it like this

Allan

robkiller

WOW thanks i was off i can see that now. I will try it thanks so much.

robkiller


tinman13kup

Is Q1 also a tip120?
Q1 designates a transistor (darlington transistor in this case) . Additional transistors would have been Q2, Q3,..etc. The actual transistor type is a TIP120 as specified in the drawing. It's no different than having R1 (resistor number 1) and having the value with it as well (220, or 10K).
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

Grumpy_Mike

WOW thanks i was off i can see that now. I will try it thanks so much.
Read reply #19 again. It is words like this you have to understand if you are going to be able to be ready to accept help. It is a good learning exercise. Words like "across" and "in line" seem to trouble beginners. They are not just fillers they have specific meaning.  ;)

allanhurst

#26
Feb 14, 2017, 04:21 am Last Edit: Feb 14, 2017, 04:22 am by allanhurst
"A picture is often as good as a thousand words."

I did a first degree in chemistry and 'systematic naming' was all the rage for defining structure.

Morphine is a complex caged molecule. Specifying it systematically took 3 A4 pages and was ( to me) totally incomprehensible.

A picture said it all.

Circuit diagrams please!

Allan



 

robkiller

Thanks so much everyone.  I learned a lot and i do agree after you pointed it out words mean something in this field and most common fillers are not fillers in this field.

robkiller

I set it up just like Allenhurt said and it works but i am only getting 6v to the 12v motor. 

allanhurst

Are you sure your supply is strong enough ? measure that too.

And if it is, the TIP120 will be getting very hot. Is It?

Allan

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