Tronic's DIY dual Mosfet H-bridge (DSMhb)

Hi,

I finished the new layout of the dual Mosfet H-bridge! With the help of EvanF I corrected many issues and after double checked everything, I can tell that this is a final version!





dual_simple_hbridge_1_2b.pdf

dual_simple_hbridge_1_2b_bottom_single.pdf


I increased a little more the distance between the mosfets and added status leds too! Now we can see the motor controller in action before hooking on it motors.

The diodes D1 - D8 that are marked as D on the PCB layout could be 1N5819 but you should do more research on alternatives as I think the correct ones to use are depending on the motor type.

The 15v Zeners are there to add a little delay on the turn-on time of the mosfets to match the turn-off time.

And finally decided to split the power sources for each bridge so one can use two different power sources, if different size motors is used. But I also did that to prevent extra current passing from the power lines, as each motor will draw from its own connector. In case you using the same power source (one car battery) for both motors, you can use a switch to turn them on, and also split the power cables like in the photo:

And to connect the power cables its preffered to use PCB cable connectors like this one:




Here is the Part list:
dual_simple_Mosfet_hbridge_1_2b_parts.pdf
dual_simple_Mosfet_hbridge_1_2b_parts.txt

There is a small error in the part list! The IRFZ44 part is actually the IRL44N model
(There is difference between IRFZ44 and IRLZ44N !!!! You need the IRLZ44N ones!!!!!!
The ones without N are not able to fully turn on by the 5v logical system of the h-bridge! )

And a small guide to assemble it:
DSMhb_1_2b_solder_guide.pdf

And one important thing:
Adding_Safety_Limit_Switches.pdf


I was thinking to try to design another version of this dual h-bridge that will use two Mosfets in parallel in place of one, to be able to handle larger amp rates without much temperature rise. The current that the device passes is based, to a degree, on the Rdson value of the MOSFET (and, of course, on the load resistance and bus voltage). In addition to being dependent on the gate drive voltage, the Rdson value will increase as the MOSFET’s junction temperature increases. So, if a MOSFET gets hot, it will pass less current because of a increasing Rdson value. Therefore, if two (or more) MOSFETs are connected in parallel, and one begins to heat up, it will eventually begin drawing less current than the cooler MOSFET of the pair, and subsequently cool down. This is assuming that all of the MOSFETs paralleled are of the same type. 100A plus H-bridge circuits can be realized with parallel MOSFETs!

More cool info on Mosfets can be found here: http://www.mcmanis.com/chuck/robotics/p ... power.html


Regards, Thanos

Thanks Thanos!

Now we dont have to buy these incredible expensive commercial h-bridge drivers :gut:

regards
Christian

Nice Job Thanos. :top:

It looks like you have even included holes for a fan! Tell me, I have a bunch of brushless computer fans, why do some work with constant DC supply and some have to be switched on and off to get them spinning continuously? They all look the same type.

EvanF

I'm curious to know what difference it would make to use pcbs with 70um copper coating.

But filling the power lines with additional solder would be safer probably.

I will as a safety precaution, after melting PCB tracks and blowing holes in mosfets I'm gonna play it safe with them.

I will use standard PC case fan on this. These fans work with 12v DC, so if your power source for the motors is 12v you can use that to power them.

I assume you refering to the new fans that CPU coolers are using! They are pulsed to be able to control easier their RPM instead of excpencive variable voltage drivers!

Regards, Thanos

Actually I forgot to say something about it! In the photos you send me it seems that you forgot to fill with solder a via hole!!!! As also mentioned in K166 manual as important thing to do!



Regards, Thanos

I saw them too after I powered up and watched it fry instantly under hardly any load (a small DC toy motor). Did you read V1 or V2 of the manual? V2 is the new manual with the zeners included. V1 did not have the zeners. I'm wondering if there is slight laziness in a crossover of design changes and they left them (the holes) on the PCB, because I bought the unit as an already assembled kit from Ocean Controls, but they wouldn't have assembled it, it would have been assembled by whoever assembles them for the kit designer 'Ozitronics'. Me not very impressed with the wafer thin PCB at all.

I bought the board to help me understand Mosfets better and to use it on one of the mobility scooters which I'm gonna mod into a gokart.

So at least I learned something about Mosfets and H-Bridges in general hey! :

*update. Just checked V2 of manual also says to fill hole. I guess on that premise I could ask for my money back! Still doesn't explain why a little motor made so much damage.. it can't have drawn too much current.

Aah I didn't realise there were 2 types. They look identical. I guess that will be something to look out for if people go buying cooling fans. So it is the older model fan that we need to source. Luckily I salvaged an old photocopier for free (hoping to find encoders) plenty of cooling fans in them, and all sorts of sizes too. I have discovered small businesses give them away as it cost money to dump them.

EvanF

What about this one?

http://www.irf.com/product-info/datashe ... f1010n.pdf

Hi,

Just an update on the SCHOTTKY diodes I might use on marked as D diodes on dual H-bridge PCB. I found that 1N5818 or 1N5819 are enouph for low power motors such as the car wiper motors are. The can handle well 15amp current in pulsed operation (PWM) and 1amp in continuous operation.

If you have any other suggestion on heavier motor types you are welcome!

Regards, Thanos

If you are going to assemble the H-bridge, there is one very important thing to take care off.

You HAVE to solder the four 2.2Kohm resistors BEFORE soldering the Mosfets on the board.

This is because mosfet gates are too sensitive to even the smallest load of current that your hands or the solder tool can produce (static electricity) and can be destroyed!


Regards, Thanos

Hi Thanos

I haven't looked into this but I was just wondering about the possibility of using on-board sockets to connect the MOSFET's, making it much easier to change if a blow up does occur. Due to the current being passed the connection would obviously have to good.

What about using a triple version of the pcb power connectors, as shown in your first post on this thread ?

The legs of the MOSFET's could be bent forward at 90 degrees, inserted into the connectors and screwed down. Still being upright the TO220 heatsinks could still be fitted.

Any sense in this or is it a non-starter ?

Hi, Roadster2

Yes this is nice idea, but I would have to redesign a new version with bigger space between the legs of the mosfets to be able to mount on it the connectors. Another problem arises then. You have to also bend apart the legs of the mosfet to be able to screw them on the connectors...

I'll check it tonight and see if its easy and convinient to alter the PCB layout like this.


Regards, Thanos


PS, I finally got in my hands the Mosfets and might try it on a breadboard during weekend! (low power motors of course yet)

I checked the possibility to use 3 legged terminal connectors (this is their name!) and it look good!

So I redesigned little the Dual simple H-bridge motor controller to accept these three legged terminal connectors and bolt on them the mosfets!



dual_simple_hbridge_1_2b_bottom.pdf (60.72 KB)

Off course it would be better if you etched the clear version (without ground plane) to avoid soldering mistakes as this high powered module can blow up easy!


dual_simple_hbridge_1_2b_bottom_single.pdf (28 KB)


Today I bought some small wire attached car fuse holder and some fuses to attach on the power cables. They are quite cheap, only 0.25 euro and another 0.25euro for each fuse. The fuses I bought are 10, 15, 20 and 30amp! This will protect both motors and mosfets from drawing too much current! I'll post some photos with them soon!


Regards, Thanos

Well, here is the wire fuse holder and some mini fuses!

Regards, Thanos

Hi Thanos

Just in case it's of interest, you can get pcb mounted fuseholders for these blade automotive fuses :-

http://www.zackfords.co.uk/product.asp?cookiecheck=yes&P_ID=127&numLanguageID=1

Also in Mini Blade versions :-

http://uk.farnell.com/jsp/Electrica...FUSE/01530008Z/displayProduct.jsp?sku=9943790

Hi Thanos,

I'm planning to build this h-bridge. I'm using standard 12v wiper motors.
Could i use for the diodes D1 - D8 that are marked as D on the PCB layout the diodes you are sugesting ( 1N4002 ) or do you need to do some more research?

Thanks RoVoR