Can I use this H-bridge

[kramer65]

I want to control a DC motor in both directions from my Raspberry Pi. So after some searching I found this DC motor, which uses a maximum of 17 Ampere.

So I searched for an H-Bridge which could handle that current and found this H-bridge which says it can handle 43A.

However, in the image below you also see that it says "Arduino". I guess that it's a generic device and that it can be used with my Raspberry Pi as well, but before buying it (and waiting a month!! for it to arrive) I want to be sure that this will actually work with my Raspberry Pi.

So my question; will this H-Bridge work with my Raspberry Pi? All tips are welcome!

[Jednorozec]

If you add a level shifter to get to the 5V that it needs on the inputs then I think it should work. You might be better off finding an H-bridge that's designed to work with the RPi.

[Gert van Loo]

I'll put in my two cents worth.
You have to check the logic chips used for the 'isolation' as they mention in the text.
But I would say your chances are 95% that it will work.
3.3 volt logic can normally steer logic running at 5V. (The other way around you get trouble).
If there are opto isolators, as they suggest, all you need to control is an LED inside the opto coupler.
The Pi can do that.

BUT!!
Are you sure you need that motor? I have no idea what you are trying to do but motors of
that size are for very professional jobs and, sorry to say so, you do not sound like a professional.
If you need a lot of power the first way to go is using a geared motor. The one you have there
will probably have a low torque on start-up but use lots and lot of current.
Then it will be rotating very fast: 30 revolution per second is A LOT (Is that what you need?)
You normally can't do anything with that speed unless you gear it down.
Yes, you can have some speed control using PWM but NOT from 18000 rpm to something useful like 100 RPM.

Otherwise: Good luck!

[W. H. Heydt]

Yes, you can have some speed control using PWM but NOT from 18000 rpm to something useful like 100 RPM.

Too many zeros...1800 rpm.

To the OP...Mr. van Loo is probably THE expert on a lot of "Pi to X" interfacing, including the "Gertduino" and "VGA666" boards.

[rpdom]

The chips used in that H-bridge seem to accept anything over about 2.5V as being logical high, so you should be ok with that.

[Gert van Loo]

The chips used in that H-bridge seem to accept anything over about 2.5V as being logical high, so you should be ok with that.

My first though was also to look up the bridge spec, but then the article mentioned an 'isolating' interface.
So my guess is that they have opto-isolators and thus you are not talking to the H-Bridge chips.

I think the main reason to go from 5V to 3V3 in the past, is that with 3V3 you can get the same logic levels for
high (>2.5V) and low (<0.8V) as 5volts so they knew 5V and 3V3 could be used mixed (sort off).
There is often logic involved but not always obvious.
A lot of people don't understand the E12 resistor series values: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82, 100...
Where do these weird values come from? until you explain about 5% tolerance and what the implications are.
(Talking about the VGA-666, that is the same reason why I chose 666 and not 555, 777 or 888....)

[rpdom]

It appears to have a 74HC244 as an input buffer. It should still work with 3.3V inputs.

[davidcoton]

A lot of people don't understand the E12 resistor series values: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82, 100...
Where do these weird values come from? until you explain about 5% tolerance and what the implications are.

In the interests of nit-picking accuracy, the E12 series is based on 10% tolerance.
E24 values are such that any resistor of arbitrary value can be labelled with a nominal E24 value and be within the 5% tolerance.

[kramer65]

@GertvanLoo - You mention some very true points there. You're right that I'm not a professional. I'm a professional programmer, but not a professional electronics engineer.

I'm just working on a pet project in which I want to build a machine which can fly a big 10 square meter kite with a machine. For this I will need a fairly strong motor. But you're absolutely right in that I probably need a geared motor. I just couldn't find any geared motors with at least 3Nm torque and at least 500rpm. Maybe this one is a better option. Or do you maybe have a tip where I can find a good geared motors?

Furthermore, as @Jednorozec suggests I guess it's easier if I buy an H-bridge which is designed for the Raspberry Pi. I guess this one works well with the Rasberry Pi, but I don't know if it can handle the current which I will need.

Does anybody know if there is a list of H-bridges which work with the Raspberry Pi? Or can anybody recommend an H-bridge which works well with the Raspberry Pi and which can handle a current of 20A or higher?

[Gert van Loo]

Let me come back to you. I have used a Chinese manufacturer of geared motors who had a huge range.
Tomorrow I will try to dig one out and see who it was.

Don't worry too much about connecting to the Pi it is not difficult at all.
For an H-bridge you need two wires per motor.
There is also a trick in that only one wire needs to be PWM .
The other just needs high-low.

I assume the motor stay on the ground?
If so your wire speed greatly depends on the diameter of the drum around which it goes.
Ideally you should work with a big diameter, that way the overlapping of the wire does not affect your speed.
But you had though about all that already not?

[Gavinmc42]

Those parts BTS or BTN796x or 798x are my preferred high current DC motor driver chips.

They work great and I always wonder why more people are not using them.
They seem to work well with the Chinese DC motor direct or geared up to 24VDC 350Watts.

However the figures you are talking about seem more like the bigger motors used for RC glider winch launchers.
For really high currents parallel mosfets are the usual method.
You can keep currents lower by increasing the voltage.
Try 36-48VDC ebike type of gear.

Mosfet drivers and isolators should work fine with 3V3 input.

[kramer65]

@GertvanLoo - A tip on a good Chinese manufacturer would be awesome. I'm so thrilled to start this project that I can't wait to order. I actually already built a first prototype 2 years ago (see pics below). The software and everything worked as I wanted to, but it was built with scrap material (an old mouse as a rotary encoder and a left over motor of an old dust buster which had virtually zero power). Because I was very busy back then I never continued with it.

So this time I thought to start off with better materials so that it can actually do what I want: fly the kite.

Anyway; looking forward to get your tip on the manufacturer!

@Gavinmc42 - So do I understand it correctly that you've been using the H-bridge I linked to for projects with the Raspberry Pi? That is good to hear, than I'll start with ordering that and I'll pick the motor later.

[boyoh]

I see no problem , using the Pi to control the H /B for the DC motor, as long as
The Pi out/put control signals are buffered to suit the H/B in/put controls signals

Advice. All programming must be wrote Fail To Safe, All isolating must be don
On the power side .and not on the low power control circuit side .
This will cover safety on the motor rotating side

[Gert van Loo]

These are the guys I used: http://www.sgmada.com/index-en.asp
I am not sure you can buy them in units. I ordered 12 prototypes. Even with considerable
express shipping costs by plane, they where still lots and lots cheaper then any motor in that
range you buy through RS or Farnell.

I have some here and the gearing is in cast iron housing. Looks indestructible.
They also do them with built-in encoder but only if you buy in bulk.

[kramer65]

@GertvanLoo - Thanks for the link. I'm not sure about those motors though. There's no mentioning of the torque and seeing the low amount of watts I would say they're not very strong. But then again; I'm really not very profi in this stuff.

Anyway, I just ordered the H-bridge I linked to above and I've sent some questions to some factories on Alibaba.com. I'll wait for them to answer and then I'll make a decision. I just want to start somewhere. If I buy a motor too strong for my use I'll simply buy a weaker one later. Thanks a million for all the information. I've learned a lot (and I really mean a lot) from this thread.

One last question; I only see mentions of gears mounted fixed on DC motors. Isn't it possible to buy separate gears and simply change them around on an existing motors when I want to? Or would that make for a fragile motor setup?

[Gert van Loo]

Some manufacturers (And I sgmada is one of them) offer the same motor with different gears.
I am not sure they sell the motors and gear separately.

One of the advantages from gears is that back driving gets more difficult.
I had a geared motor and if the hoisted load was very heavy it would come down
again as soon as the motor was stopped, back driving the motor through the gearing.
To prevent that some geared motors use a worm wheel, but worm wheels
have a very bad habit of wearing out because of the lateral friction.
(A normal gear 'pushes' a worm gear 'rubs')