Hi all,
I met a problem when I used a TIP120 to switch on a DC motor with UNO.
The diagram is attached. One digital bit is set as output, connected to the base of TIP120.
My problem is when I just power on the UNO, the motor rotates for a few turn.
I have tried to use "blank" program,i.e. nothing in the setup() and loop(), but when I press the reset bottom on UNO, the DC motor rotates.
How to prevent the DC motor rotates when the UNO is just being powered on?
Thanks for help!
Try:
What's the motor current rating ?
put the TIP120 power supply on the same power switch as the UNO.
What does this mean ?
(put it on the same ac breaker circuit ?)
Add a 10K pulldown from gate to Gnd so the pin is not floating while the Arduino starts up.
raschemmel:
put the TIP120 power supply on the same power switch as the UNO.What does this mean ?
(put it on the same ac breaker circuit ?)
Rather than having one power switch for the Arduino and a different switch for the motor PS, use a DPDT switch to control the power to both circuits.
For example if the TIP120 cct. uses a 24VDC motor PS and the Arduino uses a 7VDC supply.
Obviously the AC to each can also be controlled in a similar manor.
met a problem when I used a TIP120 to switch on a DC motor with UNO.
The diagram is attached. One digital bit is set as output, connected to the base of TIP120.
My problem is when I just power on the UNO, the motor rotates for a few turn.
I have tried to use "blank" program,i.e. nothing in the setup() and loop(), but when I press the reset bottom on UNO, the DC motor rotates.
How to prevent the DC motor rotates when the UNO is just being powered on?
This may sound silly but is it not standard protocol to initialize the uP system BEFORE applying power the MOTOR CONTROL SYSTEM ? (for ALL scenarios, so the mechanical system doesn't self destruct when you have to reset the uP ) (not to imply that the DPDT switch isn't a good idea, only that technically, it shouldn't be necessary because the uP system should have control of the ENABLE signal , without which MOST motor control systems cannot move. If the motor control system does not have an ENABLE then the uP system should have control of the motor power through a relay or contactor of some type. When you turn on your washing machine do you have to turn on a separate switch as well to turn on power to the motor ? This post is only possible because standard protocol has been ignored .
You need some circuit in between the uP and the transistor , like a poweron-reset circuit (POR) that pulls the transistor iinput to GND until the uP is fully initialized. This is a circuit that consists of a voltage comparator which, when the Vcc falls below a certain threshold OR a reset is issued, the output immediately goes LOW, (holding the transistor Base to 0 V, until the uP is fully initialized AND the Vcc is back to normal.
By definition it has two inputs
Input A - Vcc voltage
Input B Reset pin of uP
and one output
TRUTH TABLE
CASE OUTPUT
A : Vcc >= Vthreshold AND RESET pin HIGH HIGH
B: Vcc < Vthreshold LOW
C: RESET PIN LOW LOW
The transistor has and AND GATE (7408) in front of the transistor.
AND GATE INPUTS
A: OUTPUT of POR circuit
B: I/O pin used to turn ON motor.
BOTH AND GATE inputs MUST be HIGH for motor to turn ON !
Which pin are you using for the motor driver.
AFAIK, the pins default to input (floating), but e.g. pin13 might be different.
Still a good idea to add a resistor from the pin to ground (1-10k).
Leo..
LarryD:
- place a 4.7K resistor from the base to GND.
Barking up the wrong tree there - it is a TIP120!
CrossRoads:
Add a 10K pulldown from gate to Gnd so the pin is not floating while the Arduino starts up.
It is a Darlington NPN transistor. And it includes the 8.12k resistor.
Wawa:
Still a good idea to add a resistor from the pin to ground (1-10k).
Read the datasheet please!
Wawa:
Which pin are you using for the motor driver.
Now you might be getting closer to what the real problem is. Mind you, at this time of night I cannot guess it either.
We need the full circuit, we need the perfectly focused photos.
Barking up the wrong tree there - it is a TIP120!
Forgot to look at the equivalent circuit.
One digital bit is set as output, connected to the base of TIP120.
Interesting that the OP doesn't seem to be interested in PWM seems only to care about the following;
How to prevent the DC motor rotates when the UNO is just being powered on?
Forgot to look at the equivalent circuit.
(yeah, sure...) ( I shouldn't talk though. Your [Post Count/Karma count] blows mine out of the water...)