L298N can't run motor (Proteus Simulator)

KeithWalker

Joined Jul 10, 2017
2,353
I am trying to make a motor drive using L298N
But when I try it in Proteus it won't work
any Idea ?
Thank you.
The four inputs require high and low logic levels to work correctly. Your inputs have no path to ground when the input switches are opened so they never receive a low signal. Connect a 10Kohm resistor between each input and ground, then it should work..
 

Thread Starter

Sornpraram Xu

Joined Feb 24, 2019
21
The four inputs require high and low logic levels to work correctly. Your inputs have no path to ground when the input switches are opened so they never receive a low signal. Connect a 10Kohm resistor between each input and ground, then it should work..
Result is same it doesn't move
T^T
 

Zaishens

Joined May 20, 2019
28
I just don't understand when I use PWM as input signal it run but not the DC input
You see pin5 is red, meaning high. somehow the input pin to go below 1.5V, what is the voltage of that DC input?
And when you connected the 10kohm to ground, what color did the input pins have?
What if you connect them straight to ground.
What if you connect them with 10kohm to VCC and put the switch to ground?
 

Alec_t

Joined Sep 17, 2013
12,808
What if you connect them with 10kohm to VCC and put the switch to ground?
That should work, but if you want to keep the switches as pull-ups to Vcc then you need pull-down resistors with a maximum value of ~2k to satisfy the logic-low requirements of TTL circuits.
 

Zaishens

Joined May 20, 2019
28
That should work, but if you want to keep the switches as pull-ups to Vcc then you need pull-down resistors with a maximum value of ~2k to satisfy the logic-low requirements of TTL circuits.
Why 2k? why didn't it work with 10k then? only explantation would be if the inputs or the open switch are low (30k ish) impedance.
 

Thread Starter

Sornpraram Xu

Joined Feb 24, 2019
21
You see pin5 is red, meaning high. somehow the input pin to go below 1.5V, what is the voltage of that DC input?
And when you connected the 10kohm to ground, what color did the input pins have?
What if you connect them straight to ground.
What if you connect them with 10kohm to VCC and put the switch to ground?
1) The DC input is 5V when I try 2.4999V it turn to gray and If i try 2.5V it turn to red agian
But If I turn to 0.8V it turn to blue and Motor will run and if 0.801V it turn to gray and it will not run

2) With or without 10kohm if input 5V connect to ground it will turn to blue
So if both pin5 and pin7 connect to ground motor will not run cause booth input pins turn to blue

3) Same result as 2)

4) IT WORK!!!!! But why??? I don't Understand
(But If I don't connect it with 10kohm when switch is ON the input pins will turn to Yellow why?????)

Please help me explain this. Thank you T^T

Is this problem happen in proteus only?
I have never try this circuit in real life before.
If I do can I use the circuit in the first image?
 

Zaishens

Joined May 20, 2019
28
You cannot use the first image, the inputs require a defined voltage below 0.8 or above 2.5 in any situation. That's why it turns grey in between.

"2) With or without 10kohm if input 5V connect to ground it will turn to blue
So if both pin5 and pin7 connect to ground motor will not run cause booth input pins turn to blue"
This is logical, as the voltage will be close to GND potential and 5 and 7 need to have a an opposite that for the motor to turn.

"4) IT WORK!!!!! But why??? I don't Understand"
Because the pin is high when switch is open (due to 10k to VCC) and low when connected to gnd due to the switch.
This is how pull-up and pull-down circuits are supposed to work. try too google that "pull-up resistor".

"(But If I don't connect it with 10kohm when switch is ON the input pins will turn to Yellow why?????)"
This i dont understand, can you check the on and off internal resistance of the switch?
 

eetech00

Joined Jun 8, 2013
3,151
Hi

Maybe this will help.
SW is a center-off switch.
When top contact closes, motor turns in forward direction.
When bottom contact closes, motor reverses direction.
When SW is in center position, motor stops.

eT

upload_2019-5-21_20-7-17.png
 
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