# voltage amplification

Discussion in 'The Projects Forum' started by haree87, Jan 19, 2009.

1. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
hi
am trying to connect a dc motor to a controller with an output of 4 to 20 ma.... i have conveted 4 to 20ma to 1-5v..... but am not able to convert the 1-5 v dc signal vary from 0-220v dc..... am not able to figure out how to amplify it to this extent.... i have tried coltage multiplier and dc chopper.... they don seem to amplify to the extent i require.... any suggestions on what to do?????can anyone help?????

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
What power source do you want to use to power the motor?
What is the voltage and current rating of the motor?

3. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
You could use the 0 - 5 volts as a control voltage for a power supply with a rating to run that motor.

4. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
@mik

the power source is dc.....

5. ### mik3 Senior Member

Feb 4, 2008
4,846
63
How many volts? How many amps it can handle? What are power rating of the motor and what its voltage?

6. ### italo New Member

Nov 20, 2005
205
1
you guys miss the point he want so he says to convert 1-1.5v dc to 0-220vdc. VARIABLE. good luck

7. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
@mik

the motor is actually to be used as a cooler... so i have connected wings to it...... let me give u the blowers spec....

capacity-125 m^3/min
its ratings are 5 amps
235V
350Watts
duty cycle is continous

8. ### mik3 Senior Member

Feb 4, 2008
4,846
63
350W/235V=1.5 Amps

Why do you say 5 Amps? Is the efficiency of the motor only 30% ?

What power source you want to use?

9. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
@ mik

yes mik it shud be only 30% efficient.... the power source is DC.....

and the prob i have is, this blower was only provided to me for my project.... now i gave u the ratings that were on the tag plate on the blower... so i guess i don think i can change that.....
btw.... would using a triac do any good??? i was thinking of changing the firing angle to vary the voltage to the blower.....

any ideas?????

10. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Triacs and SCRs are for AC.

Use a MOSFET or IGBT to switch the ground side current, using PWM. You'll need a flywheel diode across the motor, cathode towards V+.

You won't get all the way from 0% to 100% PWM; more like around 3% to 98% - but it should be good enough.

11. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
u sure this would be able to deliver 0-220V????

12. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
u sure this would be able to deliver 0-220V????

and can u give me more details on this???? am not getting a clear pic of ur idea

13. ### mik3 Senior Member

Feb 4, 2008
4,846
63
If your mains voltage is 240V and you rectify it directly you will get a no load voltage of 339V after the filter capacitor.
Have in mind that is dangerous to work with the mains voltage if you are novice in this stuff. Take care please.
Then drive an IGBT or MOS with PWM and you will be able to control the average voltage fed to the motor.
Don't forget to put a fast recovery diode in anti-parallel with the motor as Sgt said.

For more information on PWm and motor control have a look here:

14. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
i am not an expert in working with 240v... but i do have help.... i have ppl who are experts help me..... thanks a lot for the help and the link.....

15. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
You need a 220V DC supply first. This isn't too difficult.

Then you need a PWM circuit.

Where are you? Do you have 220V available? Or do you need to make that avalilable?

16. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
i am in india at a university.... so i guess gettin these stuff wont be very difficult