Continue to Site

# DC Motor Speed Control

Status
Not open for further replies.

#### gauravkothari23

Hi All.
I have attached a circuit diagram, where i am planning to control the speed of 180V 360 Watts DC Motor using N76E003 Controller.
I am using a traic to control the AC phase line with the help of Zero crossing detection, and the same output of triac i am converting to DC to drive and control the speed of DC motor.
I just need to confirm if the circuit and logic i am using is reliable solution to control the DC Motor.

#### Attachments

• 180V Motor Driver.png
36 KB · Views: 185

Hi,

I don´t like the big capacitor at the output of a voltage regulator.
It needs a huge amount of energy to charge it.
The big reservoir should be on the input side of the regulator. The fast capacitor should be on the output side.
A 100uF is not fast enough to supply fast current pulses

Do a simulation:
Replace C1 with the 1000uF and C2 with a tiny 1uF ceramics.
--> It´s more stable regarding HF .. and still will keep 5V longer at valid levels than the 470uF/1000uF circuit.

***
I compare the input and output capacitor situiation with this:
* Imagine you have a 10 liter bucket to maintain the level of a bathtub.
* Then imagine it the other way round: A full bathtub of water to maintain the level of a 10 l bucket.

Klaus

Hi,

I don´t like the big capacitor at the output of a voltage regulator.
It needs a huge amount of energy to charge it.
The big reservoir should be on the input side of the regulator. The fast capacitor should be on the output side.
A 100uF is not fast enough to supply fast current pulses

Do a simulation:
Replace C1 with the 1000uF and C2 with a tiny 1uF ceramics.
--> It´s more stable regarding HF .. and still will keep 5V longer at valid levels than the 470uF/1000uF circuit.

***
I compare the input and output capacitor situiation with this:
* Imagine you have a 10 liter bucket to maintain the level of a bathtub.
* Then imagine it the other way round: A full bathtub of water to maintain the level of a 10 l bucket.

Klaus
Yes Sure KlausST.
will replace the capacitos will lower value as suggested.
Is it reliable to use the motor controller drive as per the circuit. will it work properly
Any suggestions..??

Hi,

I don´t have enough experience with: AC -> triac -> rectifier -> DCMotor
But I guess a snubber won´t hurt.

Klaus

Hi,

I don´t have enough experience with: AC -> triac -> rectifier -> DCMotor
But I guess a snubber won´t hurt.

Klaus
for snubber, i would be using BTA16 SW - 600V. because as per the datasheet, it is mentioned snubberless.
--- Updated ---

what are the chances of back EMF damaging the Triac

Last edited:

what are the chances of back EMF damaging the Triac
No chance, it's clamped by BR3.

No chance, it's clamped by BR3.
Thanks FvM.
I need one more suggestion. I was also planning to go control the same DC motor using a different design.
Rather than using triac and control phase angle, can I use mosfet. Circuit would be something like.
220V AC ----> BR3 -----> N Channel Mosfet -----> Motor.
Can drive the motor using mosfet and PWM using MCU.
Which one is more reliable. Triac circuit or Mosfet Circuit
--- Updated ---

But I guess, in the case of mosfet, special care has to be taken like adding snubbers and flyback diode to avoid mosfet getting damaged.
Can I use one more bridge rectifier between mosfet and motor to make no chance for EMF to damage the mosfet.
Will the extra bridge rectifier work.

Last edited:

in the case of triac design, how can i control IN RUSH CURRENT. do i need to implement it in hardware or can be controller by software.

Hi,

As long as the motor is not stalled, just use a ramp on phase angle.

If you want a true current limit, you need to measure it. And decide how to handle it.
There are several reasons why to limit the current:
* limit torque
* protect motor winding burn
* protect triac
Each has it's own rules ... some need true RMS, others need average current limit.

You have to decide

Klaus

Hi All.
I have attached a circuit diagram, where i am planning to control the speed of 180V 360 Watts DC Motor using N76E003 Controller.
I am using a traic to control the AC phase line with the help of Zero crossing detection, and the same output of triac i am converting to DC to drive and control the speed of DC motor.
I just need to confirm if the circuit and logic i am using is reliable solution to control the DC Motor.
Hi

Is it a hubby circuit or industrial project? Most of DC motors has it is own power driver.

Hi

Is it a hubby circuit or industrial project? Most of DC motors has it is own power driver.
It's a industrial project.

Suggest input capcitor of regulator higher than output capacitor as it store energy after rectifier. 1000uF input and 100uF output capacitor.
Add high frequency 100nF decoupling capacitors to input and output of regulator, place closely to regulator as posible to reduce ringing/ output ripple.
Add 100nF decoupling capacitor to Vcc & GND of MCU, place closely to MCUas posible to reduce radiate EMI.
All unused GPIO should connect to GND, don't floating them.
Should sense directly AC zero crossing instead through transformer.
All net from GPIO of MCU should be short as possible.
Add damping capacitor to zero detect pin to ignore noise when motor run, suggest < 1nF, place closely to GPIO in as posible.
Add TVS or R, or Inductor before input capacitor of regulator to reduce spike from AC source. Regulator can't not clamp fast trasient/surge voltage.
Add damping capacitor for button < 100nF.
Should have indepent watchdog to reset if MCU hang, or on/off switch to reset MCU.
Layout should have large clearance for isolation and between low&high voltage.

Reliability has some levels. Your design is not prefer for higher level because it is too simple. It has no input & output current protection, when start motor the start current quite high, it can damage triac. So, the firmware need to increase slowly on duty instead of open full. When output short circuit, it will bloom .... Your circuit must have at least one fuse for input. Better when implement 02 fuses, if output short to Earth.

Status
Not open for further replies.