# Are there any microcontrollers with integrated H bridge for DIY servo?

I want to build my own servo system. It will get a PWM as input then move an object according to this input. I have a motor, potentiometer feedback, microcontroller with separated H-bridge.

Since I need a lot of these I want to use an IC with both H bridge and microcontroler on same chip. Like the one we find in servos.

Are this chips available for sale, or are they made by servo manufacturer for their own use ? Are the PID parameters (Pi, Di, Ki) inside changeable ?

Question edited after Wouter van Ooijen comment.

• Read the datasheet, its says (only) "H-bridge". – Wouter van Ooijen Jul 23 '13 at 14:12
• Do you really believe you can build servos for cheaper than you can buy them? Or do you have some oddball requirement that no commercial servo can meet? – Dave Tweed Jul 23 '13 at 15:02
• I need accurate, low strenght but very fast linear servos. I did not found any, so I make them using motorized faders wich come without electronics. The final servo will have 20cm stroke. The fader manufacturer told me they can build custom models for me for the quantites I want. If you have any better alternative in mind feel free to tell me. – bokan Jul 23 '13 at 16:20
• You said "I want to use an IC with both H bridge and microcontroler on same chip. Like the one we find in servos". Do you have a link to this device? – Andy aka Jul 23 '13 at 16:23
• I don't have any ref, that's the purpose of this question ! :) I just see that there is only one chip in servos, so it must contain both. – bokan Jul 23 '13 at 22:06

There are some (expensive) components like FreeScale Semiconductor's MM908E625 HC08 (Motorola compatible) microcontroller, which are purpose-built precisely for the kind of use expressed in the question. The headline description of the MM908E625 is:

"Integrated Quad Half H-Bridge with Power Supply, Embedded MCU, and LIN Serial Communication".

To quote from the tech note: (all bold marks are mine)

Features

• High-performance M68 HC908EY16 core
• 16 KB of on-chip flash memory & 512 B of RAM
• Internal clock generation module
• Two 16-bit, two-channel timers
• LIN physical layer
• Autonomous watchdog with cyclic wake-up
• Three two-pin Hall effect sensor input ports
• Four low RDS(ON) half-bridge outputs
• One low RDS(ON) high side output
• 13 micro controller I/Os

In short, this is perfect for bidirectional control of up to 2 low power (500 mA) DC motors or one stepper motor via the dual integrated H-bridges. A PID can be implemented in the microcontroller core, it has ample memory and a 32 MHz internal clock, more than enough for a PID. The PID can incorporate rotary position input from up to 3 Hall Effect sensors. Also, Back EMF detection is built in, which allows improved motor control. My preferred use for the ADC would be temperature input, allowing over-temperature shutdown to be implemented.

Sample code is available from FreeScale for basic PID functionality, including BEMF and encoder sensing.

Some more advanced open source PID implementations for the HC08 cores are around, though I am not aware of any already ported to this device. Will porting be complicated? Not really.

It is worth contacting FreeScale for samples, and to check whether they sell an evaluation board as well.

For other, similar products, try keywords like integrated core and H-bridge.

Note:

Using a part like this, sourced at low volumes, is unlikely to be cost effective compared to sourcing even off-the-shelf hobby servos, since servo manufacturers enjoy economies of scale.

Update:

If actual PID is not required and simple comparator-type actuation against position encoder input is sufficient, there are other cheaper options. However, these will typically not allow soft-actuation (slow start / slow stop / overshoot tuning).

• Mitsubishi M51660L, a single DC motor (or solenoid) driver for servo applications. $3 apiece on eBay. • Infineon TLE4206, another single DC motor (or solenoid) driver for servo applications.$4 apiece on eBay.
• Thank you for your nice answer (this time ;) ). These chips are more expensive than using a tiny MC + H-bridge + assembling them on PCB. This is the information I wanted. – bokan Jul 23 '13 at 22:21

[PLEASE NOTE: The question was altered AFTER I answered! Check the original post before you get cranky and down-vote! Sheesh!]

The motor driver you selected doesn’t have any “brains,” it is merely a device to control the speed and direction of the motor depending on the input control signals.

A (very) simple servo control system diagram:

The project you’re developing is one of those you work bassackwards on. You know the load to drive, then you must select the gearbox, motor and position feedback device. (A potentiometer might be fine for very light use, say 100 operations a day, maybe 20 days a year, but will wear down to the nub rapidly if used 100’s times a day for months on end! You’ll be looking at a magnetic rotational position sensor or optical position sensors (http://en.wikipedia.org/wiki/Rotary_encoder) – something that will not wear out in a couple of days!)

Next comes the “brain.” A microcontroller (or equivalent device, the "MCU" in the datasheet you provided) that will compare the input [control] signal (where you desire the output to land) to the actual position of the output shaft. The “brain” calculates the difference between the input and actual position then orders the motor controller (h-bridge/amplifier) which way to turn (and in some instances, the speed to get to that position) known as PID (http://en.wikipedia.org/wiki/PID_controller).

[I do not know of a single integrated circuit package (IC) containing both a MCU and h-bridge. SEE EDIT BELOW FOR LINKS:]

• Thank you for the comment about reliability of potentiometters. I need several movement per seconds 12 hours a day. So I will have to choose another option. But my question still unanswered : "is there any IC with integrated H-Bridge ?" – bokan Jul 23 '13 at 14:29
• -1 for no attempt to actually answer the original question. – Joe Hass Jul 23 '13 at 15:09
• You'll notice he changed the question after I answered. I do not know of a single integrated ic containing both a MCU and h-bridge. – JoeFromOzarks Jul 23 '13 at 15:19
• -1 for the implication that your not knowing about something existing, is definitive in any way, regardless of whether such a part exists or not. – Anindo Ghosh Jul 23 '13 at 17:18
• @AnindoGhosh Thank you for your observations. You'll note that my answer was applicable to his original question and I'm too lazy to repost an undated answer to his updated question. Can you specify a part meeting his specifications? – JoeFromOzarks Jul 23 '13 at 17:33

I don't know of any microcontrollers with the H-bridge built in, but there are some, like the pic 18fxx31 line that have some enhancements to make motor control systems easier. These tend to have quadrature encoder interfaces built right into them so you don't need interrupts to handle every increment and noise handling is dealt with. They also have enhanced PWM modules that are designed to make some of the trickier aspects of H-bridge control easier (though I personally haven't had to use that aspect)