A 5v switch to a 12v motor???

Hi guys,

Sorry about my dumb topic title, i didnt know how to explain it.

I'm thinking of buying one of these usb servo development boards called phidgets:

**broken link removed**

--- you can see it does more then servos, you can plug LEDs stright into it etc.

It outputs +5vs when on, and 0v when off.

The motor i want to control needs 12volts -- how would it be possible to use the +5v from the "phidget" to work as a switch to control the motor?

I dont know if i'm explaining it right? if not please let me know.


Apart from the one that outputs 5volts, there is one that use's external power from devices, but i dont know if it would be enough:

Inputs are activated by 4 to 30 Volt signal. Outputs sink up to 30V at 2A. The outputs do not provide power they just act as switch to ground.

Click to expand...

found here: **broken link removed**

If anyone could explain (or give a link) on what im trying to do it would be great.

Regards.

itsallgood said:

Hi guys,

Sorry about my dumb topic title, i didnt know how to explain it.

I'm thinking of buying one of these usb servo development boards called phidgets:

h**p://www.phidgetsusa.com/tutorials/tutorial2.asp

--- you can see it does more then servos, you can plug LEDs stright into it etc.

It outputs +5vs when on, and 0v when off.

The motor i want to control needs 12volts -- how would it be possible to use the +5v from the "phidget" to work as a switch to control the motor?

Click to expand...

My first question is are you wanting a digital or an analog drive? Is the motor either off or on, or is its speed being controlled by varying the DC across it.

If it's digital, all you need is the max current of the motor and a suitable transistor to source or cutoff current to the motor.

If it's analog, you're going to need a linear translation, using, perhaps an op amp that can also drive a low impedance (a motor) load at higher current. (If so, I'd suggest looking at the OPA power op amp series of formerly Burr Brown.)

itsallgood said:

I dont know if i'm explaining it right? if not please let me know.


Apart from the one that outputs 5volts, there is one that use's external power from devices, but i dont know if it would be enough:

Click to expand...

As I see that, this means it can accept a higher outside current source and switch it to the load, your motor etc. (This means we're probably talking about a digital thing, a bang bang on/off operation.)

itsallgood said:

Inputs are activated by 4 to 30 Volt signal. Outputs sink up to 30V at 2A. The outputs do not provide power they just act as switch to ground.

Click to expand...

found here: h**p://www.phidgetsusa.com/cat/viewproduct.asp?category=1000&subcategory=1100&SKU=1012

If anyone could explain (or give a link) on what im trying to do it would be great.

Regards.

Click to expand...

That sounds like an open collector situation. In other words, there is a transistor with an open collector terminal in the device, and to get it to switch your load, your load will need to be tied to a higher potential, so when the transistor switches on (tries to take the collector voltage low) your load will feel your source potential across its terminals.

In other words you'll want something like

V+ ---- (+) motor (-) ----- open collector output

However, (no, I haven't clicked to see the device) you contradicted yourself:

itsallgood said:

It outputs +5vs when on, and 0v when off.

....

Outputs sink up to 30V at 2A. The outputs do not provide power they just act as switch to ground.

Click to expand...

Either you're talking about two separate outputs or two different devices, for you've described an active high and low output. You may have misunderstood??

Take a look at the attached picture ..
It shows how to control servos and dc motors using 0-5V logic ..
Servos and Motors can be rated for much higher voltages, for example 12V, but the control inputs accept any standard TTL/CMOS logic level ..

Outputs sink up to 30V at 2A. The outputs do not provide power they just act as switch to ground.

Click to expand...

This can indicate that the output (OC - open collector, or OD - open drain) can withstand voltages of up to 30V dc and can sink currents (to 0V) of up to 2A ..

Regards,
IanP