I've also noticed the P6KE68CA diodes seem to be letting 2.5 out of 3V through while testing, will this lead to a shoot through in the live system?

Those are transient voltage suppressors, which aren't the same thing as fast recovery diodes. The schematic seems to be relying on the body diode/parasitic diode in the MOSFET for spike suppression, which they aren't very good at. It's best practice to use a Schottky diode across source and drain, cathode/stripe toward positive.

If the MOSFETs are switched on, they need to be switched off as well, otherwise the gate charge will hold them in the same state. So a high and low signal are needed for each gate, rather than a high signal and no signal.

 

Ok, so I have the H-Bridge portion of the system working, but I'm having some trouble with the IC.

Right now I have the ground of the Arduino connected to the common ground for the Arduino, H-Bridge and IC, but that seems to make the system act weird.

Do I need a separate ground for the arduino, or do I need to connect the link between the Arduino pin and HIP4081 pin to a resistor & ground to drain unwanted voltage when it's turned off?

 

Need something more specific than "acting weird" to even guess at the problem.

Tell it, in a stern voice, to behave?

 

When the IC is connected to only the arduino 5V source, and no other power source the voltage between the arduino and IC is fine (5V). When I connect an external 18V source the current becomes 2.8V when the pin is turned off and 0V when the pin is turned on.

 

The inputs are floating, When connected to the Arduino, it will pull them high or low, though you can use 100k pull down resistors to keep all inputs at zero until a voltage is applied.

Try that and it should be stable.

Then try having the motor spin in just one direction with the driver inputs (no PWM, just forward), for 5 seconds and then stop (coast). Make sure the driver IC and MOSFETs do not get hot. Then do the same for reverse, if all is good, proceed to 5 seconds of 50% duty cycle PWM forward, check temp, 50% PWM reverse, check current, etc.

Monitor temps closely, general rule of thumb: If you can't hold your finger on a component for over a few (3-5) seconds, it is running too hot. If the motor spins and all is good thermal wise, you should be ready to go.

 

Connecting the pin to a resistor & ground seemed to fix the problem. It still floats somewhat, but I think I can fix that by changing the resistor.

Now I'm having a problem with the IC :/. To debug the system would disconnecting BHS, AHS, BHO, BLO, AHO, and ALO then connecting BLO to ground with a voltage meter between it and ground work?

 

I'm confused still.

What is "The Problem"? Does it work with the tests I suggested above?

If not, what were the symptoms?

 

The solution you listed seemed to fix the hanging problem. There is now near 0 volts when the pin is on low, and around 4.8 volts when the pin is on high.

Now I've run into another problem where the IC does not seem to be triggering the MOSFETS even though it's receiving an input signal. Right now I'm trying to eliminate variables to find the cause of the new problem.

 

What are you sending it?

Can you draw a schematic of exactly how it connected, after VERIFYING your connections with an ohm-meter?

 

so the problem was the disable pin was not set to low -.-, but the voltages still seem a bit off

Test Voltages
condition
BLI: HIGH
ALI: LOW
DIS: LOW
BHO: .5V
BLO: 11V
ALO: .3V
AHO: 0V

Here's the schematic I'm using to see if the IC works
http://switchit001.com/voltage_test.png

EDIT: I'm not sure if that schematic is right, if not is there anyway to test the IC independently of the H-Bridge?

 

The IC may need to be connected to MOSFETs to function correctly, that's why there are the sense resistor inputs, and other feedback paths.

 

Ok, I've connected the IC to the H-Bridge and it does not seem to be turning the MOSFETS on/off :/ (a volt meter in the middle stays at 0). I have made a few changes to the system so maybe a change caused the problem. (http://switchit001.com/h-bridge_new2.png)

-I removed the LDEL & HDEL pins
-I attached Disable to the ground rail
-I changed the 100 Ohm resistors to 10 Ohm resistors
-I'm using a 1N5822 intead of the BYV (http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_177990_-1)
-I placed a volt meter between the grounds and battery for safety (if there are any surges the fuse will break)


To test the system I am connected the BLI and ALI pins to either the negative or positive rail, then turning on the power supply. I think the problem may be the volt meter between the ground and battery, however I don't want to remove it until I know it's the problem. I'm also thinking the 1N5822 may be too restricting too much current, if that's the case I'll have to buy/use a different diode.

 

#1) Why did you change out the components?

#2) You have a Voltmeter in SERIES with the power rail? Or is it an Ammeter? Voltmeters do not pass current very well, think of it as a 1 Meg Ohm resistor in the link.

For testing, set the inputs to "coast" on the H-Bridge and apply power, measure voltage, you may see a few millivolts, but it shouldn't swing to 18V or -18V.

If you've never worked with an H-Bridge before this, please try a hobby motor and an L298N H-Bridge Board (<$10, often <$5 for assembled board with headers), plug into your arduino and make the hobby motor work. Then measure the same signals on the L298 that you have in your high current H-Bridge above.

I'd suggest doing the L298 first if you've never worked with interfacing voltages or driving motors before.

 

Hello,

I am doing a 8VDC motor, although the voltage is smaller, the principle is similar.

I use microcontroller to control forward and reverse, if you don't need speed control and the response time is not critical. Just forget the using
mosfets and using two relays.

My circuit contains two relays of DC coils voltage 12V, output rate at 10A at 240VAC/28VDC, cost around $1 each, inexpensive... they are driven via a NPN transistor.

Don't know if it suits for yours,

Regards

 

#1) Why did you change out the components?

#2) You have a Voltmeter in SERIES with the power rail? Or is it an Ammeter? Voltmeters do not pass current very well, think of it as a 1 Meg Ohm resistor in the link.

For testing, set the inputs to "coast" on the H-Bridge and apply power, measure voltage, you may see a few millivolts, but it shouldn't swing to 18V or -18V.

If you've never worked with an H-Bridge before this, please try a hobby motor and an L298N H-Bridge Board (<$10, often <$5 for assembled board with headers), plug into your arduino and make the hobby motor work. Then measure the same signals on the L298 that you have in your high current H-Bridge above.

I'd suggest doing the L298 first if you've never worked with interfacing voltages or driving motors before.

1. For the 10ohm instead of 100ohm resistors, I talked to a few people and they thought 100ohm would be too high.
The two suppliers I bought the parts from did not offer the BYV so I had to use a different diode
2. It's a volt meter, and during the H-Bridge with no IC tests it did drop the voltage down to less than 50% of it's original value

I tried switching the 2nd volt meter to amp meter mode, but that did not seem to help much :/. I do have a small motor and a low voltage IC one of my friends sells so I will try to test the voltages with that.

 

Hello,

I am doing a 8VDC motor, although the voltage is smaller, the principle is similar.

I use microcontroller to control forward and reverse, if you don't need speed control and the response time is not critical. Just forget the using
mosfets and using two relays.

My circuit contains two relays of DC coils voltage 12V, output rate at 10A at 240VAC/28VDC, cost around $1 each, inexpensive... they are driven via a NPN transistor.

Don't know if it suits for yours,

Regards

That may be the better option for this project. I do have about 4 relays I'm not using so I'll try to get a schematic drawn up to see if such a system would work.

 

Ok, so I did a bit of research, and I think you would still have a problem jumping the amperage from 50mA out of the Arduino to 50A in the H-Bridge if you were only using relays, however you did give me an idea for conrtolling the 4 fets with two relays...
http://switchit001.com/h-bridge_new3.png

 

Ok, so I just checked the voltage of the IC alone, and the 2nd volt meter draws too much for it to run at all. Would putting a 1uf capacitor between the h-bridge and battery prevent a shoot through at low amps?

 

I'm unsure where the confusion is if you use the circuit posted on the previous page.

The Datasheet for HIP4081 H-Bridge driver covers all of these parameters, the IC provides dead time to prevent shoot-through, and other faults.

H-Bridge control and MOSFET high side driving are all part of that IC, so changing values from a known working schematic without testing it first will only cause more confusion and problems that could be avoided by following the datasheet application note. A functional circuit is shown on page 13 of that datasheet.

 

I'm unsure where the confusion is if you use the circuit posted on the previous page.

The Datasheet for HIP4081 H-Bridge driver covers all of these parameters, the IC provides dead time to prevent shoot-through, and other faults.

H-Bridge control and MOSFET high side driving are all part of that IC, so changing values from a known working schematic without testing it first will only cause more confusion and problems that could be avoided by following the datasheet application note. A functional circuit is shown on page 13 of that datasheet.

The relay schematic I posted was an idea I had from raychar's post. It's seperate from the HIP4081A, and I'm prob not gonna use it unless i can't get the HIP4081 to work.

As for the 1uf capacitor, it would mainly be meant to protect the system from any mistake I might make that would cause a shoot through. The final system would not have it.

Also I just moved the volt meters around (one where the motor will be, and one directly after the h-bridge, but not after the IC grounds), and I am now getting a reading of about 4V in the middle (0V directly below the H-Bridge) when no MOSFETS are turned on. Do you know if that's just a normal reading from the IC or if there's a problem with it?