Analog output through USB 6008 to drive dc fan motor

[johnsold]

The circuit I posted will not damage your fan.  The voltage might go slightly above 12 V but no by enough to hurt anything.  Coq Rouge's circuit could go to as high as 16-17 V, but even that would probably not damage the fan unless allowed to run for extended amounts of time (hours).  The LM317 circuit can handle currents to about 1.5 A with proper heat sinking, so handling the power of your motor should not be an issue.

Note that parts of this discussion mentioned PWM, but these circuits are for continuous (variable DC) control as the USB-6008 is not fast enough for reasonable PWM control of motors.

Lynn

[sufre]

Thanks, John for prompt reply.

So you are not recommend this circuit to be used for my application? If so, do you have any circuit that suitable for my requirement, I am looking for several circuits, but not confident which one to use, since it is general and I am not good in electronics. It is difficult to judge which one.

As from the circuit, is the IC called LM317? and the LM317PA is what?

Thanks in advance

Kind regards

Sufre

[johnsold]

Sufre,

The circuit should work fine for you.  I just wanted you to understand that it is a continuous analog circuit and not a switching PWM circuit.

The LM317 (with various suffix letters) is an adjustable voltage regulator IC.  The suffix letters designate different packages and temperature ranges and may differ slightly with different manufacturers, so check the data sheets from the manufacturer your will be using to get a suitable combination.

Lynn

[sufre]

Hi John.

I hope we are referring the same circuit diagram, LM317 USB6008 motor.png 12 KB. In this diagram I saw there is an IC (no labelling) which is I am referring to, and the other one is LM317PA.

Kind regards

Sufre

[johnsold]

The IC with no label is an op amp.  Nearly any op amp will work.

Lynn

[sufre]

Thanks, a lot.  In that case I will use the available LM741 OpAmp, and

LM317T 1.5A ADJUSTABLE VOLTAGE REGULATOR

Is this ok?

[johnsold]

Yes.

Lynn

[sufre]

Hi John.

Can you check my circuit diagram, I am not sure with the connection on LM317 and Lm741.

Here attached the circuit diagram for your reference.

Kind regards

Sufre

[johnsold]

Sufre,

That is a good start.

1. You do not have power connections to the 741. Pin 4 goes to the negative supply and pin 7 to the positive supply.  These are not explicitly shown on the diagram I posted, but are necessary for the circuit to operate.

2. R3 should be a 1 watt resistor.  The size you have shown on your layout looks like a 1/4 W resistor.  At 12 V output this resistor will dissipate 0.6 W.  A 1/4 W resistor would soon burn up.

3. The spacing of the traces near the pads for the 741 is very small.  On the image they touch.  This will short out your circuit and at least cause it to malfunction if not to damage components.

Lynn

[sufre]

Hi John

Thank you for your effort in looking up the circuit diagram with clear explanation. However I still have one question regarding with Diode 1 which was written 1W.

Is is Zener diode? If I want to order, what specification should I write?

Here attached a modification circuit diagram to finalised and to be shared among the committee.

Kind Regards

Sufre