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Topic: Please help me with this nightmare 0.03mA (Read 1 time) previous topic - next topic

latif

My output pin from arduino is 4.9v and 0.03mA
I'm trying to use transistor to drive 12v and 3.5A to the water pump motor!
But it doesn't fully tun on it's turn on and off all the time and it gets so hight in few sec. I also tried darlington pair but didn't work.
My project do within two weeks and I'm having nightmare when I sleep that I'm not going to get it work.
Someone suggessted adruino motor shield but I never worked with it and it seems hard to do it that way!
Also I bought relay rw-ss112d that has 5pins but the current it needs to opearate is way higher than the current I have!
My transistor is NTE152, if there is a better transistor to buy I don't mind to buy it.

So please help me!!!

Benji

To know what is going wrong, there are a couple of things needed:
1: Do you have a schematic?
2: Show your code
3: How have you measured this? What points in your circuit, with or without load, what readings are you expecting?

latif

my red wire coming from arduino uno smd pin0. The multimeter reading is 4.9v and 0.03mA, then to a resistor 1k ohm, and then to the B pin in the transistor.
all grounds connected together.
http://hotfile.com/dl/114874193/1db3b7b/photo.JPG.html
http://hotfile.com/dl/114874243/4f87f8b/photo_(4).JPG.html
http://hotfile.com/dl/114874272/8d6965b/photo_(1).JPG.html
http://hotfile.com/dl/114874299/208d518/photo_(2).JPG.html
http://hotfile.com/dl/114874326/d791890/photo_(3).JPG.html

latif

here is the reading for current and voltage.
http://hotfile.com/dl/114874826/98a709b/photo_(6).JPG.html
http://hotfile.com/dl/114874885/7521491/photo_(7).JPG.html

AWOL

#4
Apr 18, 2011, 12:20 pm Last Edit: Apr 18, 2011, 12:28 pm by AWOL Reason: 1
Quote
0.03mA

Did you mean 0.03A?

30uA is going to need a massive hfe to switch 3.5A

From the transistor datasheet, hfe2 (VCE 5V and IC3A) is only 15.

Would a TIP120 be a better choice?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

latif

I only have 0.03mA as it shows in the pic, and TIP120 require base current 120mA! Will that work!

James C4S

I'm not sure how to open the pictures you posted.  (I'm not a fan of any site that requires me to join in order to view.)  I'd suggested using something imgur.com which is free and easy to use.

When you are measuring current, does your multimeter require you to move your test leads?  When measuring voltage you must be in parallel to node and when measuring current you must be in series.

On my multimeter (and most I have seen), the Voltage and Current measurements require moving the lead to a different connector.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

AWOL

#7
Apr 18, 2011, 04:57 pm Last Edit: Apr 18, 2011, 05:09 pm by AWOL Reason: 1
Quote
and TIP120 require base current 120mA!

Last time I looked, the TIP120 has a gain of something like 1000.

EDIT: The 120mA comes under "maximum ratings" for base current.
With a gain of 1000, you should require only 3.5mA for your load.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

latif


Quote
and TIP120 require base current 120mA!

Last time I looked, the TIP120 has a gain of something like 1000.

EDIT: The 120mA comes under "maximum ratings" for base current.
With a gain of 1000, you should require only 3.5mA for your load.


but what i have is 0.03mA?
is this normal output reading for arduino!!!
cuz in the specifications of the hardware it says output 40mA?

retrolefty

Quote
but what i have is 0.03mA?
is this normal output reading for arduino!!!
cuz in the specifications of the hardware it says output 40mA?


How much current flows from an arduino output pin is determined by what it is wired to. That 40ma value is the maximum current rating for the pin, not it's actual value, again that is determined by what your have wired to it. If you indeed have only .03ma flow then something is wrong with your wiring or resistor or transistor. You do have a ground wired between the arduino board and the negative terminal of the 12vc supply? That is a requirement.

Lefty

elandd2011

Is bad idea to drive a bipolar transistor with collector connected  to 12 volts and base connected trough resistance to ardu,you have to add some protection

latif


Is bad idea to drive a bipolar transistor with collector connected  to 12 volts and base connected trough resistance to ardu,you have to add some protection

Did u see the diagram!

elandd2011


latif


BenF


My output pin from arduino is 4.9v and 0.03mA

The above statement is not making sense

If you set pinMode to output, the AtMega is capable of sourcing current up to several hundred milliamps (doing so however would destroy the microcontroller).  You can source up to 40mA and still stay within specifications. At 40mA, this would require a BJT transistor with a modest gain (less than 100) to drive a 3.5A load. A better choice however might be a logic level power MOSFET.

One possible explanation for your issue is that you forgot to set pinMode to OUTPUT. In this case current is sourced through the internal AtMega pullup resistor and this limits current drive capability to somewhere in the microamp range.

Another issue is with the power supply, you need to make sure it is capable of supplying in excess of 3.5A.

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