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1  Using Arduino / Project Guidance / Re: Choice of temperature switch on: January 08, 2014, 07:07:35 pm
i picked the 45 degree module.
2  Using Arduino / Project Guidance / Re: Choice of temperature switch on: January 02, 2014, 02:17:04 am
Never mind i have figured it out.
3  Using Arduino / Project Guidance / Choice of temperature switch on: January 02, 2014, 02:15:24 am
Hie everyone i am using 4  MOSFET powered electronic speed controllers to control 4 motors in a 4wd robot. The controllers are bound to get hot during use and i prefer to have a cooling fan switch on when temperatures reach a certain point, rather than have a fan running all the time.

The switches turn on after their rated temperature has been reached and turn on a fan.
I have a choice of 50 degrees, 60 degrees, 80, 90 and 100 degrees Celsius. Is 60 degrees Celsius decent enough or do i have to select a higher rated temperature switch?
Thanks.
4  Using Arduino / General Electronics / Re: Best half bridge driver with shoot through protection for h bridge. on: December 28, 2013, 07:37:06 pm
Quote
I think the IR-2112 (and other bridge drivers) do have the anti-shoot-through time delay that you are referring to. This prevents the high side mosfet and low side mosfet from being on at the same time.

thanks i will have a look  at that and see.

Quote
At low speeds you can engage mild reverse drive levels to hasten stopping, you will
need to detect actual motor speed for this.  A PID control loop is a good way to
manage speed control here I think.
i have through of that. but i was worried that it might create some current spikes that can damage the mosfets.
5  Using Arduino / General Electronics / Multiple l298N motor drivers in parallel on: December 28, 2013, 03:09:12 am
Just a question of interest. Is it possible to connect lets say 5 l298n motor drivers  in aprallel to make a 10A dual driver? 20A total?
6  Using Arduino / General Electronics / Best half bridge driver with shoot through protection for h bridge. on: December 27, 2013, 11:48:54 pm
I am trying to make an n channel h bridge motor driver with an electronic brake function. I have tried following this tutorial but im left confused as to whether the driver will  make the motor stop rapidly as it would in e.g an l298n h bridge driver, just by setting the SD pin to LOW (Which shuts down the h bridge driver). As i know that setting the "HIN"  and "LIN" pins to high will short out my battery and fets.

Later in the tutorial is  shown that the HIN from the from one half bridge is connected to the LIN of the other and LIN is connected to HIN  to enable the use of two pins.  As shown by the image uploaded below. Will that enable me to set both pins to HIGH to "brake" the motor (not regenerative braking). without destroying  the system?
7  Using Arduino / Programming Questions / Re: Issues with "digital read" for two sensors on: December 23, 2013, 07:50:31 pm

Quote
Don't you suppose that it matters how the switches are wired? I do.
each motor has its own limit switch.  limswitch 1 is not working  limswitch 2 works. i have even put limswich 1 in the pins of limswitch 2 and it worked. i think the issue is with the code.
8  Using Arduino / Programming Questions / Issues with "digital read" for two sensors on: December 23, 2013, 07:08:27 pm
hie i am trying to use two switches as bumper switches  on my robot., one on each side. The problem is that one switch only works. Each motor initially is running at maximum speed. After each switch is hit each motor reduces its speed for 3 seconds before each returns to its maximum speed.

EDIT: only limswitch2 works the other just keeps running at max speed even if its switch has been hit.

Code:

//I am using the Arduino Mega 2560 R3
int limswitch =41;
int limswitch2=39;// define limit switch and allocate its pin
int ENA=51;//Enable for motor controller at pin 51
int RPWMA =45;//RPWM
int LPWMA =43;//Left pwm
int ENB = 53;
int RPWMB = 47;
int LPWMB = 51;
int led= 13;//default arduino led.

void setup()
{
 pinMode(ENA,  OUTPUT);
 pinMode(RPWMA,OUTPUT);
 pinMode(LPWMA,OUTPUT);
 pinMode(led,OUTPUT);
  digitalWrite(ENA,HIGH);  
 analogWrite(RPWMA,0);  
 digitalWrite(LPWMA,HIGH);
 digitalWrite(ENB,HIGH);  
  analogWrite(RPWMB,0);  
  digitalWrite(LPWMB,HIGH);
  
}
void loop()
{
  
int switch1 = digitalRead(limswitch2);//define the limit switch as switch 1
  if (switch1 == HIGH)//if the pin reads 5v
  {
    //run motor for 3 seconds at 50% power
  digitalWrite(ENA,HIGH);  
  analogWrite(RPWMA,100);  
  digitalWrite(LPWMA,HIGH);
  delay(3000);
  //return to max speeed
  digitalWrite(ENA,HIGH);  
  analogWrite(RPWMA,0);  
  digitalWrite(LPWMA,HIGH);
}
int switch2 = digitalRead(limswitch);//define the limit switch as switch 2
  if (switch2 == HIGH)//if the pin reads 5v
  {
    //run motor for 3 seconds at 50% power
  digitalWrite(ENB,HIGH);  
  analogWrite(RPWMB,100);  
  digitalWrite(LPWMB,HIGH);
  delay(3000);
  // return to max speed.
  digitalWrite(ENB,HIGH);  
  analogWrite(RPWMB,0);  
  digitalWrite(LPWMB,HIGH);  
  }
}

9  Using Arduino / General Electronics / sending two pwm signals to h bridge using a Servo pulse to PWM converter on: December 20, 2013, 08:36:09 pm
Hie everyone
i was wondering if it is possible to send two pwm signals to a h bridge built using FAN7093 half bridge chips, which are exactly the same as the common BTS7960 h bridge:
http://www.ebay.com/itm/Dual-BTS7970-68A-Motor-Driver-Drive-Module-H-Bridge-PWM-Control-robot-projects-/171080096646

The two signals will be generated from an rc receiver pulse and converted to pwm using this tutorial.
http://bobblick.com/techref/projects/sv2pwm/sv2pwm.html

the same person built his own transistor h bridge and used this with no issues but id like to confirm before i mess up my FAN7093 driver ic h bridge.
thanks.
10  Using Arduino / General Electronics / Determining the right mosfet current for a h bridge. on: December 19, 2013, 07:19:37 pm
Hie again. i am about to place an order for some n channel mosfets for my h bridge and there is a few things id like to verify.
i will be making a 4wd robot with skid steer configuration using 4 motors, so there will be 2 h bridges, one controlling 2 motors.
Since my motors stall  at 42A each, will a 120A for each h bridge be enough? or is 80A enough since these motors are quite impossible to stall?

here is my chosen Fet
http://au.element14.com/jsp/search/productdetail.jsp?sku=2253787
11  Using Arduino / General Electronics / Re: Are Diodes Necessary in a H bridge circuit for motor braking? on: December 18, 2013, 07:26:49 pm
I found the answer i was looking for on the web. it turns out that another chip i was looking at has a logic that prevents "shoot through" and provides electronic brake to the motor without blowing up the circuit or shorting the battery.

Here is a link to the tutorial:
http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge
12  Using Arduino / General Electronics / Are Diodes Necessary in a H bridge circuit for motor braking? on: December 17, 2013, 07:28:30 pm
Hie i am trying to build a mosfet motor driver using the schematic sourced from a fellow forum member.  The schematic is the attachment i uploaded below. Do i need protection diodes for motor braking as indicated by those red squares and are they facing the right way? Thank you.

The website i sourced this schematic is:
http://tahmidmc.blogspot.sg/2013/01/using-high-low-side-driver-ir2110-with.html
13  Using Arduino / General Electronics / Re: Huge voltage drop across transistor H bridge on: December 15, 2013, 08:46:23 pm
Quote
The circuit show at reply #6 was using all N channel MOSFET.

I may have overlooked that one. I will have look. With the mosfets i have chosen i will need 10v to fully switch them on.  I think i will have to use BillHo's idea. I will do some more research into this.
14  Using Arduino / General Electronics / Re: Huge voltage drop across transistor H bridge on: December 15, 2013, 07:15:00 pm
Quote
You can, but for 80A you would be better off using all N-channel mosfets. This is because it's easier to get N-channel mosfets that have good characteristics for high-current switching.

Thanks for your help  sir.

Is it possible for you to link me to a recommended circuit diagram or show me how to set up a system with all n channel  mosfets?
Thank you
15  Using Arduino / General Electronics / Re: Huge voltage drop across transistor H bridge on: December 15, 2013, 05:37:40 pm
Quote
To build an 80A H-bridge, you need to use four or more N-channel mosfets, with specialised gate driver chips that provide a floating gate drive for the upper mosfets, and provide an idle time (when both upper and lower mosfets are off) to avoid shoot-through. Good circuit layout will be very important. This is most definitely not a project for a novice.

so i cant make a h bridge using 2 n and 2p channel mosfets, just like with bjt transistors?
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