USB6008 and PWM to control heat element

[duff79]

Hi all,

I nee a little assistance with a project im completing. I have to control the temperature of a heating element using PWM.

When i have the hardware sorted out i will be trying to create a labview PID program to control the heating element around a desired setpoint.

Here is the basic list of components i am using and i will attach a rough diagram to show how i have them connected up.

1. NI USB-6008

2. 12Vdc  PWM controller  http://www.dhgate.com/12v-24v-3a-dc-motor-speed-control-pwm-hho/p-ff808081317fdb680131821f26066bcb.h...

3. SSR Crydom EL Series Solid State Relay 100Vdc, 10A

4. 35Vdc heating element

I have done some research on the forums here and understand that using theUSB6008 for PWM is a non-starter. So I want to use a analogue output from USB6008 as an input into the PWM control board and then ill be able to adjust the duty cycle using a dial. This PWM controller will then be used to switch the SSR, turning the heat element on/off.

The issue i currently have is that this controller will not function with the analogue output from DAQ. I realise that the USB6008 only supplies an output voltage max of 5v, so i need some suggestions of how to boost the analogue output voltage so it can power this controller.

Any suggestions will be much appreciated

[SnowMule]

An IC known as an "op amp" will amplify voltages... wiki's got a great article on them.

[BB.]

Hi Duff79,

An op-amp would allow you to boost the voltage from the USB6008, as SnowMule said.

What is the PWM controller expecting from the USB6008? Will a certain voltage give a certain result from the PWM board?

Regards,

[duff79]

The idea is to use a thermocouple to monitor temp of heat element. I wanted to control the heating element with Pwm but using Pwm control board instead of labview as usb6008 not ideal. I want to be able to select a set point and then reach set point and stable state as quick as possible. Not sure wether to use analogue or digital output to "power" Pwm controller. I need a 12v for Pwm controller input for 12v Pwm output which is used to switch a SSR.
I have used a 528 Op amp as suggested and this has powered board but from some reason the Pwm signal is between 8 and 12v.

Thanks for help so far.

[NamHKim]

I am currently tackling a similar task. I set up a heat tank to maintain a desired temperature, monitored by a thermocouple, fed into PID inside LabVIEW, then its output is used to 'Generate Signal' inside LabVIEW to make PWM signal, which toggled an SSR connected to a heat tank's heating element. I didn't use a external PWM controller, since LabVIEW was able to make the PWM signal. I got it working up to +5, -3 degrees to my set temp. The overshoot was asymmetrical due to the asymmetrical heat capacitance, so I hooked the dt out from PID control to use different PID variables when its heated up then cooling down, resulted little better set temperature. Since its a heating element, with very slow response (my gain was 35~45), it was little hard to nail it compared to mechanical element. I used LabVIEW 12, with compactDAQ 9485 (SSR) and 9211 (thermocouple) in 9174 chassis.