Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Microcontroller that control high voltage or....

Not open for further replies.


Newbie level 4
Jan 30, 2009
Reaction score
Trophy points
Activity points
high voltage microcontroller


If we want to control our a high voltage system or big mechanical devices, electric motors by using microcontrollers or PCs., how must we design it so we can protect our low voltage microcontroller based boards.

I am trying to learn is there a specific(or conceptual) name that i can look up whose job is making "safe" bridge between high voltage system and low voltage controller.

Any information, keyword, link that explain design step of that part is welcome.

Thanks in advance...

microcontroller controlled low and high voltage

You'll need to provide some more details, else, you can use opto-isolators.

high voltage microcontroller control

I agree, the solution is to use opto-isolators.

Basic idea:

Your controller produces a signal that lights an LED when it wants to operate a power switch.

The LED is actually embedded inside a light-proof plastic package which also contains a light sensor. There is no physical connection between LED and sensor but the light from the LED can cross a gap and reach the sensor. The gap gives you the isolation, potentially up to several thousand volts and also prevents unwanted interference from the motors getting back into the controller.

The sensor side of the opto-coupler is connected to suitable power switches which then drive your motors.

If you understand, please explain it to me. :)


microcontroller voltage control

I didn't know that. Yes, opto-isolators. Like that one.

If someone design a microchip. Its name is vlsi-cmos design. It has a conceptual name. Or someone design software, we called programmer and there are lots of subcategories.

Now, Details of my questiion...

For example, you are working in a company, and your client(say, an shipping company) wants you to make a system that they can control their ships giants motors by a computer.

Now there is a big mechanic structure(or a big electrical structure) and a PC or microcontroller system that works with low power.

Here who makes decision about which devices to be used to connect 2 systems.
What are the devices? Names, types... I mean do they have general name, general development steps?
What are the criterias?

I mean, there is a big system and you developed a software and upload it to the microcontroller, but how can you make connection between microcontroller and system, by what type of devices?

low voltage microcontroller

That is a difficult question to answer, it depends on the situation.

Normally, the company needing the equipment, or a contractor supplying equipment to them would draw up a precise specification. It would state exactly what motors or other electrical loads have to be controlled, for how long and under what conditions the equipment is activated. That specification would be passed to an electrical or electronic engineer (or team) who using their experience and knowledge of available parts would design, build and test the equipment.

For example, the specification might say:
Supply is 3-phase 440V at 50Hz.
Three single-phase motors to be switched. Switching to occur at zero volts.

Motor 1 controls, vertical motion of a crane, maximum load 3KW. Extent to be limited by mechanical switches. Position setting is by joystick in crane operators cabin.

Motor 2 controls rotation of crane about vertical axis, maximum load 5KW. Angle of rotation determined by steering wheel in crane operators cabin. Rotation to be limited to 200 degrees clockwise from reference point and 50 degrees anti-clockwise from reference point.

Motor 3 extends crane boom, maximum load 4KW. Extent limited to 1.5 metres from operators cabin to 12.3 metres at full extension. Control by lever in operator cabin.

Opertional temperature range -20C to +50C under 90% humidity.

That is much shorter than a real request!
It would be up to the designer to work out how the control linkages work and how the motors are actually switched. Usually, there would be much talk between designer and the end user to optimize the system for their needs.

The name for the person or team that do this is "Application Engineers". Typically, they would design it using the best technology then look at ways of reducing costs so they fall within the allowed budget. Other engineers may be involved to design certain parts of the whole system, such as software engineers, environmental engineers and mechanical engineers.


74244 connection to 8051

use relays and heavy duty contactors, quite standard in industries

switch high voltage with microcontroller

use H-bridge circuits with motors.
buffers & latches like 74244 &74373
opto couplers
driving transistor
power electronics components like thyristors, opto TRIAC, TRIAC's
also use diodes and zener diodes as protection to ur circuit

microcontroller relay high voltage

If you follow 'elrayes' advice make sure you use the high voltage versions of 74244 & 74373. Normal 5V ones will not be adequate. elarayes will advise you on where to get ones that work on hundreds of volts.



Use of the Relays Depends upon the driving Ampere rating of the Load. So choose the adequate relay to drive the load without any chattering. & Use the POwer driving for the relays too using the ULN2803 etc.


Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to