Harkhka

modified 9 years ago

H bridge

143

268

05:33:43

Can someone please tell why this is not working.. 
*Update*

The P channel Mosfets are Numbered as 1,3 and the N channel Mosfets are Numbered as 2,4.. All the logical cases are as follows where 1 represents that Mosfet is conducting and 0 represents that mosfet is in high resistance.. 

- Not Running 
- Not Running 
- Not Running 
- Short Circuit
- Not Running 
- Brakes
- Motor Rotates Left
- Short Circuit 
- Not Running 
- Motor Rotates Right
- Brakes
- Short Circuit 
- Short Circuit
- Short Circuit 
- Short Circuit 
- Apocalypse 

For P channel Mosfets, the gate should be grounded for them to conduct and the two pull up resistors are connected to gate to stop the conduction after removal of signal.. 

For N channel Mosfets, a gate to source voltage Vgs must be applied which must be greater than threshold voltage for the Mosfet to conduct any current and two pull down resistors are connected to gate to stop the conduction after removal of signal.. 

published 9 years ago

hurz

9 years ago

The motor model should be simplified as ~1.2Ohm

Harkhka

9 years ago

Really sorry sir..I provided the wrong link.. My bad.. Here is the correct link: https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://ixapps.ixys.com/Datasheet/98755.pdf&ved=0ahUKEwiSx9f-uZ7NAhUCJJQKHdufAqEQFggiMAA&usg=AFQjCNEiuR_kW09NE_vem62RyylcK_YNKg&sig2=s_zto0SUHiZtFIlSWZAaVQ

Harkhka

9 years ago

And the video I am following is: https://youtu.be/Lzxuro0Z2Ew

Harkhka

9 years ago

hurz

9 years ago

This new MOS spec is even worse Vgs=10V for Id=13A and Rdson=200mOhm.

hurz

9 years ago

This video is far away from explaining the difficulties of a pure n-mosfet bridge!

Harkhka

9 years ago

Sir, check the Vgs threshold.. Its minimum value is 2V and maximum value is 4V, so the mosfet will conduct with Vgs of 2V-4V..

hurz

9 years ago

@harkhka, read the spec again. This 2 to 4 V is the threshold, whilch is measured at 4mA! You are talking for your motor of 9000mA! This mos need Vgs 10V or even more.

hurz

9 years ago

Btw, you haven't made any update to this circuit here. For me its getting a bit annoying. Missing pulldown. Motor load is still 1uH and not a resistor. The Mosfet model is not updated and still a completly unrealistic test version. How do you want to continue?

Harkhka

9 years ago

Sorry for the late update sir.. Sir I'm very confused regarding which moss to use and which I shouldn't.. Sir, please guide me..

hurz

9 years ago

Ok, i can see now you have updated the circuit. What we need is a load which is close to worse case 10A to your motor. 12V/10A=1.2Ohm right? The first MOS seems to be better for this job. Anyway, you have to understand what the problem with both top side mosfets exist! Lets see...

Harkhka

9 years ago

I guess that the problem with those top mosfets is that their induced channel is tampering and not flat.. Only a guess..

hurz

9 years ago

No they are identical to the low side once. Again, check the difference of whats a common source circuit and whats a common drain circuit. You still dont see the difference?

Harkhka

9 years ago

Unfortunately no sir 😢.. It's the first time I'm practically using mosfets.. I really need some expert advice..

hurz

9 years ago

Play around with this circuit till you have questions or understand whats the differences. http://everycircuit.com/circuit/6566480977592320

Harkhka

9 years ago

Oh, now i got your point sir.. The two upper mosfets are used as high side switches and to turn them on, a voltage greater than Vcc (approx Vcc+Vt) must be applied.. And the two lower mosfets are ised as low side switches and to turn them on, only a voltage greater than Vt is necessary.. So, if I make this then I will face a problem in driving my motor with complete 12V supply..

Harkhka

9 years ago

This video really helped me get this thing.. https://youtu.be/g8I_upSEGz0

hurz

9 years ago

Now you got it!!!!

Harkhka

9 years ago

😀😀😀😀

Harkhka

9 years ago

Sir, what should I do to solve this problem..?

Harkhka

9 years ago

Instead of those two upper N channel mosfets should I use P channel mosfets instead..?

hurz

9 years ago

To use a pmos would be to easy 😉 but for price and performance there are also good reasons to use 4xNmos. Check this http://everycircuit.com/circuit/5723454646517760

Harkhka

9 years ago

Sir analysing this complete circuit is a bit complicated for me 😞.. I need a simple motor driver unit which I can control with my microcontroller ☺

Harkhka

9 years ago

Sir will this work..? http://everycircuit.com/circuit/6624514693136384

hurz

9 years ago

Yes, but put a base resistor for the BJT once in series e.g. 4.7kOhm. See the current of 5V control logic about 2A!!! Arduino can only drive about 20mA

Harkhka

9 years ago

Done sir.. Now is it okay?

hurz

9 years ago

Ok, and think about the control pin (from arduino pwm?) You need an inverter. PWM pin directly at one half bridge e.g. left pair and an inverted PWM signal for the right side. But you have to find a way to stop the motor. What i can imagin is to writeAnalog to one pin for pwm and in case you need stop change pinMode to input. But this would still cause the inverted signal to be in opposite. One might use an EXOR to have an comfiguable inverter/or no inverting, by use of second input. So need some brainstorming about the logic!

Harkhka

9 years ago

Can I make change in the gate voltage of those n channel mosfets if I want to change speed..? Like if I want at full speed then I can provide a gate voltage much above Vth and if I want to decrease speed then I can provide a gate voltage clossr to or little below Vth.. Will this work..? Just a thought..

Harkhka

9 years ago

Because in that youtube video that guy used a normal fade program to run a motor.. So can I also do the same..?

hurz

9 years ago

No! This will burn the mosfet!

hurz

9 years ago

Before starting with a dual full bridge, you should finish the logic part around for a single bridge or even a half bridge.

Harkhka

9 years ago

Sir can you please tell from where I can read about them..

hurz

9 years ago

Make a logic table for all gate voltages and check which states are allowed and which are not or even dangerous! Comment each line of state comibnation and publish your results here.

Harkhka

9 years ago

when Vgs = 2v..the channel is formed and minimum drain current will flow..

Harkhka

9 years ago

As Vgs increases the drain current increases.. When Vgs reaches 4V the drain current will be maximum

Harkhka

9 years ago

anything above 4V is not allowed and is dangerous..

hurz

9 years ago

No no no. What i was talking about is a Logic table and not an analog thing. Number all for gates from 1 to 4. And combine all 2^4 = 16 states were one gate can logicaly just have zero volt or 12V! We dont care what voltage might cause between 0 and 12V. Only cares what logicaly is needed to understand.

Harkhka

9 years ago

Oh, I got your point sir.. So I've labelled the upper Mosfets as 1,3 and the Lower Mosfets as 2,4.. So the cases are :

Harkhka

9 years ago

0000 = Not Running

Harkhka

9 years ago

0001 = Not Running

Harkhka

9 years ago

0010 = Not Running

Harkhka

9 years ago

0011 = Apocalypse

Harkhka

9 years ago

0100 = Not Running

Harkhka

9 years ago

0101 = Brakes

Harkhka

9 years ago

0110 = Motor Runs Left

Harkhka

9 years ago

0111 = Apocalypse

Harkhka

9 years ago

1000 = Not Running

Harkhka

9 years ago

1001 = Motor Runs Right

Harkhka

9 years ago

1010 = Brakes

Harkhka

9 years ago

1011 = Apocalypse

Harkhka

9 years ago

1100 = Apocalypse

Harkhka

9 years ago

1101 = Apocalypse

Harkhka

9 years ago

1110 = Apocalypse

Harkhka

9 years ago

1111 = Alien Invasion

hurz

9 years ago

Ok, please put that logic table to your description. This way the mos is conducting=1 and mos is in high resistance=0. In parallel to this it would be nice to have a translation in volatge for Vgs of each mos type. E.g. pmos need to be connected to ground to conduct and nmos needs 12V at gate to be low in drain source resistance. Most power mosfets are rated in spec by Vgs 10V for maximum continues current at drain. We have 12V, which is also ok, as long we dont go over the maximum, which is for most mosfets +-20V. Some can handel +-30V or only +-15V.

Harkhka

9 years ago

Done Sir

hurz

9 years ago

Great, translation?

Harkhka

9 years ago

Done that too.

hurz

9 years ago

Now its time to get rid of this manual switch in your circuit and reduce the voltage of the rectangle source to arduino uno 5V. This one is suppose to be for PWM to turn the motor left. A second PWM signal to turn right.

Harkhka

9 years ago

Like this sir..?

hurz

9 years ago

First, arduino signals are ground referenced. So put one end of generator to ground and switch only between 0V and 5V (i still guess you have arduino uno). Second, you now drive the motor left, right, left, right, left, ... , damaged? You need two modes, one left on/off and one right on/off. At least 2 digital control pins!

Harkhka

9 years ago

Yes sir.. I just wanted to show about both modes so I put +5V and -5V under one signal 😝.. But now I've corrected it ☺

hurz

9 years ago

Ok, Vgs for pmos is 12V. Thats fine, but the nmos just get 5V. Better you double check this what Vgs you need to get highest possible current, and lowest resistance for them! 5V is for most mosfets to low at 10A you target.

Harkhka

9 years ago

Actually I need 20A..because the two motors of each side will be connected in parallel and will be controlled by a single H bridge.. :)

hurz

9 years ago

take the Nmos model i gave you which is much closer to a realistic mosfet then this model you use here.

hurz

9 years ago

BTW i tested this circuit with irf4905 and irf540 as nmos. In a half bridge combi (your combi 1 and 4 only) just to see i can ramp such a motor smoothly. Its woring fine without any extra cooling. However my motor already starts running at 1A and my powersupply is limited to 5A. I also added a shunt resistor to measure the current and limit the current a little. With this i can stop the motor if current gets to high. Some kind of secure stop. The nmos needs Vgs 12V with 5V Vgs i'm pretty sure it will quickly burn!

Harkhka

9 years ago

So sir if the mosfet will burn at 5V gate-source voltage then how can I control the bridge with a microcontroller..? 😞

Harkhka

9 years ago

And again thank you soo much sir that you are doing this much for a completely unknown person from guiding me at every point to testing in real life.. Thank youu soo much ☺☺

hurz

9 years ago

You have 12V available. Put one more common emitter NPN and you can make 0-5V to 12-0V like an logic inverter.

Harkhka

9 years ago

Like this Sir?

hurz

9 years ago

No, more like this 😊 http://everycircuit.com/circuit/6211116843139072

hurz

9 years ago

Here we go https://youtu.be/Oolo17B2Zx8

Harkhka

9 years ago

That's a very nice video sir and this is exactly how I want my motors to run with speed variation.. But I'm finding it a bit difficult to analyze the completed circuit together (not much experience in electronics :p) .. But this circuit works exactly like I wanted and I'm really interested in understanding its working.. Sir please fetch me with some knowledge.. ☺

hurz

9 years ago

Most things you need are already here. Im quite happy with the pmos performance IRF4905 but still looking for a better Nmos which is getting a little to hot to finaly drive 10A. Have you made a decision on which Nmos you take?

hurz

9 years ago

I can recommend IRLZ34N cuz max Vgs is 10V but it is also working at Vgs =5V close to lowest resistance. This will simplify the circuit I have tested, cuz there can be the extra inverter be removed.

Harkhka

9 years ago

Okay sir.. Then I will use IRLZ34N as it will work fine with arduino.. ☺☺

Harkhka

9 years ago

Sorry for replying late.. I just got my new laptop so I was busy writing and learning some codes.. 😀😀

hurz

9 years ago

Lets see if its working fine, cuz 5V is the lowest voltage were this mosfets starts to perform. Still better is Vgs 10V.

Harkhka

9 years ago

So, shoud I provide 10V Vgs using transistor as switch..?

hurz

9 years ago

Build a half bridge and test the mosfet duo. Maybe you are happy with 5V for Vgs for the Nmos. Do you have the Motor already ordered? The motor info, link you provided, looks a bit strange. So size and power seems to not fit to my feeling. To much power for this little thing.... 9A at 12V. I have a similar looking one, but it used by far less current. Max 120mA in stall condition!!!

Harkhka

9 years ago

I will buy the motors from market, not online.. 12V with stall torque of 12kgcm

Harkhka

9 years ago

There is very nice drive motor sizing tool which helps us to calculate the type of motor we can use for our robot car.. http://www.robotshop.com/blog/en/drive-motor-sizing-tool-9698

Harkhka

9 years ago

For the worst case scenario, I entered mass = 5Kg, Number of motors = 4, Radius of Drive wheel = 0.4m, Robot Velocity = 2m/s, Max Incline = 60°, Supply Voltage = 12V, Desired Acc = 1m/s², Efficiency = 60%.... For, this data it shows Angular Velocity = 477.71rev/min, Torque = 8.06kgcm, Power = 39.5W, Maximum Current = 3.29A and Battery Pack = 6.59Ah..

Harkhka

9 years ago

So, I also think that 9A written for that motor was incorrect..

hurz

9 years ago

I agree. Wow, a big project!

hurz

9 years ago

Btw, do me a favour and update this circuit. I dont like your latest emitter follower update which I said makes the 5V at gates even lower then 5V. Connect them directly or with lets say 47Ohm to arduino output. Arduino can easily drive 40mA on a single pin but it depends on gate capacitance and frequency for PWM we haven't talk so far. So still many things to learn for you. I will follow your next steps and try to give you as much assistance I can.

Harkhka

9 years ago

Removed those transistors from nmos.. Was travelling a bit so couldn't update on time.. :)

hurz

9 years ago

Great, this is now more or less the circuit I have tested. However, there is still a long way to go :-) here a first prototyp https://youtu.be/WbzFH911r1A

Harkhka

9 years ago

It's so good sir.. 😍

Harkhka

9 years ago

Is it the same circuit as above..?

hurz

9 years ago

You missed to update the pmos model/parameter.... anyway thats ok for now

Harkhka

9 years ago

Yes sir.. Now what should I study for this circuit..?

hurz

9 years ago

Maybe start with a half bridge if you have all components. Or even just a quarter bridge (single mosfet as in one of the first videos you linked here) get some feeling, and in touch with hot components.

hurz

9 years ago

Expecting soon first visible results from you!

Harkhka

9 years ago

Will be going to buy components soon.. which nmos and pmos should I finalize sir?

Harkhka

9 years ago

Sir..?

hurz

9 years ago

http://everycircuit.com/circuit/6008431355363328

Harkhka

9 years ago

Hello Sir.. I was really really tensed while you were gone and didn't came online for these many days.. I kept thinking about you as you are very active in EC and post many circuits so I was really worried about you not posting anything for soo many days.. I'm glad you are back.. Is everything fine sir..?

Harkhka

9 years ago

While you were away I went to the market and got the components.. It was very difficult to get any pmos model so I bought a dozen of nmos (irf540n)..

Harkhka

9 years ago

Firstly I tried them in a quarter bridge in low side config as you suggested and they worked without any problem.. The motor was receiving around 12.45V (12.6V supply) with gate-source voltage of 5V.. The results were the same with gate-source voltage of 12.6V..

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