how to control dc motor speed using 4 to 20 ma

[adurai]

i am doing a project - dc motor speed control using computer control by instrumentation software....from the computer the output is 4 to 20 ma current..by using that i want to control the dc motor circuit which run at 36 v dc...i need the control circuit..can anyone pls suggest any idea please

 

[IanP]

In the first step convert 4-20mA to 1.0-to-5.0V using 250Ω resistor ..

In the second step, apply this 1-5V control voltage to voltage controlled P(ulse) W(idth) M(odulator) = PWM ..

Here are details of the voltage controlled PWM:
https://pcbheaven.com/circuitpages/Voltage_Controlled_PWM_Generator/
https://pcbheaven.com/circuitpages/Triangle_Wave_Generator

To drive a motor use a power MOSFET see picture below) or power BJT ..

Rgds,
IanP

 

[adurai]

mostly i got it.....but other than PWM and microcontroller? just by using 0 to 5 v ,is it possible to control or vary or adjust the external 0 to 60 v dc? like a switch?

 

[karesz]

Hi,
Whay isnt OK a pwm for you, then if you use switched DC, is in reality a PWM like controlling?
You can control a FET/Transistor analog too , but in that case you will have much energy as heat to dissipate_with pwm it will be only a small protion to do...
K.

 

[frankliner]

You could also do it analog if efficiency is not a concern.

You can use RCV420 from TI to convert 4-20mA to 0-5V. Then you can use this 0-5V to feed the reference voltage for a discrete voltage regulator. Choosing the gain with the resistor divider will allow you to set the scale of the motor voltage. The motor would be connected from the regulator output to gnd. Don't forget the freewheel diode.

 

[adurai]

but our motor start to run at 24 volts dc with a minimum speed 600 rpm and maximum speed 2300 rpm at 48 volts dc....this 24 to 48 volts may be extrernal supply...i need a control circuit to control this dc voltage using 0 to 5 volts input