Im stuck into this ground leveling problem. I´m building an H-bridge circuit using L298N IC. Arduino will control the logic for enable pins of the h-bridge, and I will use PWM at logic pin...
Let me explain the problem:
H bridge has two Voltage inputs (one for motor feeding, say +18V, and other for enable signal +5). If I use arduino to feed enable pins and a SEPARATED battery to feed motors, I must level battery grounds (arduino ground and battery ground)... is that right?
Couldnt it be dangerous since there could be an potencial difference between grounds? How can I do that?
I dont want any current/voltage problem between logic circuit (arduino) and high power circuit (motors and Hbridge) - since motors do make current to vary a lot, it could be a problem and plus motor current is too high.... So, if the two circuits are eletrically connected, it can be a problem.. isn´t it?
One idea I have is to use the same battery for logic and load (motors), but control de current to logic with an otpcoupler (tipically 4n25) wich is enabled by arduino. This way arduino would be totally isolated from heavy load, but then I would have another problem: design a voltage divider to put 5v to enable pin from the 18v battery. Its not complicated (its easy actually), but using the voltage divider, the current flowing to logical pin could be high... How can I do that in that case?
Thanks! Thats sounds a little too newbie, but what type of file is that? It looks like a HTML but I cant open it in a regular web browser... Im I missing something?
Hey! This fritzing app is great for arduino based schematics! Very cool. thanks.
Now, let me see if I understand your idea. The catch is to use only 1 battery to feed arduino and the motors, so the leveling problem would be naturally solved. But to feed arduino use a voltage regulator instead of a raw voltage divider. Is that right?
But what about the oscillating current caused by motor varying torque and velocity (the greater axis resistance, the lower motor total resistance and the bigger the current from battery to circuit. The greater the motor speed, the lower the current). I think current can reach 1A at start and stays in 0.5A in maximum speed. Does that voltage regulator IC handles this current variation? Cant it damage arduino?
Well, I see many many posts about teing all grounds together all the time, but no one seems to care about potencial difference between batteries. Is that difference really an issue?
Hi
the circuit is like a filter,if the battery is far from the motor add some capacitor like 100uf/50v very near to the motor(s), all oscillating problem will be filtered for the circuits
elandd2011:
Hi
the circuit is like a filter,if the battery is far from the motor add some capacitor like 100uf/50v very near to the motor(s), all oscillating problem will be filtered for the circuits
By circuit you mean the voltage regulator? Why would battery distance make a need for the capacitor? I understand how capacitors filters voltage oscillations, but the "far from battery" part I´ve missed.
Does that has something to do with the total resistance of the wire? Can you explain that?
Sorry about the number of questions.. I just can´t just use something.. I got to understand so I can go sleep at night withou being thinking of it in a loop.. lol
if you use large cables from battery to motor(s) or to battery to arduino board you will have parasite inductance , the capacitor will compensate it, the long cables introduce"noise" and the capacitors will filtering it, the noise comes from the AC network in every place like homes or in industrial environment (very noiseless),in your case motor will introduce lot of noise and in this way you will reduce it. .Real circuits are no "ideal circuit", means a cable is not only a cable.We can go very deep in theory. A cable is a resistance plus inductance plus a capacitance between everything near to the cable itself and depend how long the cable is, and how thinness is and material of the cable,even all this cable parameters depend of the working frequency.
Large cable is more than maybe 50 cm, so is good idea use this capacitor always
the "circuit" mean the circuit i sent to you, remember keep the correct polarity .
go it???????????????
Totally got it! The wire works a little like a 'antena' (ampere law) capturing electromagnetic interference from environment and transforming part of that energy into current, isnt?... Cool.
You helped a lot! Thank you very much! I´ve ordered some 7805 voltage regulators I´ll continue the work now I have enough info.
One more thing.. do you have a good reference (book) in electronics? I know enough math to understand a little deeper, so Im willing to get a good book. I have some pratical books here but they lack of theory.. Im looking for something that goes deep enough but not deeper
