What to use to Power Solenoids? 3A total power draw from 4 solenoids

Methinks you have the wrong forum.

I just realized I failed to include, this is being driven by an MSP430.

Google "solenoid driver circuit schematic"

there are several DRV88xx devices that would fit this application.

Great on the DRV88xx. I saw something about a PCB that had places for a MSP430 and the driver.

Question, would I need heat sinks? I'd assume I would.

we have many 88x devices that can do 3A+ w/o heat sink

Great! In this case I have 4 switching solenoids (uni-directionally activated on power and inactive with power off. Each eats around .8A. What would be a good choice from the 88 family?

I have 3.3V control signals coming from the MSP430.

Your cheapest solution is the ULN2003 driver.  Use 3 outputs parallel for each solenoid. 

You may need to use 1 chip per solenoid if the package runs too hot.

The MOSFET solution needs 3V gate rating. Try IRLML6246TRPBF   RDS(on) max (@VGS = 2.5V)   66 mohm

Peter

Also look at the DRV8803/4/5 for solenoid drive.

Just to be clear, these solenoids are basically like relays (normally closed I believe and open on power). So they only need to move one direction as far as polarity is concerned.

Would those be able to run 4 x 0.8A through one chip without a heat sink?

The discrete MOSFET   IRLML6246TRPBF   will dissipate 0.07W at 1Amp.

You will need to add 100kohm gate resistor to ground and 1N4001 across the solenoid.

Peter

Nick,

Please check out the link below to the datasheet.  The device is available in two package types.  The larger SOIC can do 0.8A x 4 continuous.  If you want a little more margin, the PWP can do 1A x 4 continuous and has an exposed pad on the bottom that can dissipate heat into a thermal ground plane on the PCB.  

http://www.ti.com/lit/ds/symlink/drv8803.pdf

Great, it sounds like that will be the way to go for this project.

Are there any issues connecting the MSP430's outputs directly to the inputs of the DRVxx chip?

Lastly, if I want to have a visual that the solenoids are getting power, what is the best way to do that with LEDs? Could I just put an LED in parallel with each solenoid (and of course a current limiting resistor in series with each LED)?

Thanks to everybody who's chimed in. Looks like I have a nice small footprint solution.

I'd like to add a final word of caution regarding the heat-sinking.

The power dissipated in each DRV8803 output is about 0.5W (Using 0.8A and 0.75 ohms )

The 2W total power dissipation is significant for this size of device. Pay close attention to the PCB heat-sinking guidelines in the data sheet.

If the 2W is not acceptable then consider using 2 DRV8803 devices in parallel. 

Peter

Looks like the discrete component will generate much less heat. I may try it both ways and see what gives better results.

There is a built in diode across the output on the IRLML6246TRPBF. Is it not a good idea to rely on this against flyback voltage spikes?

I just tried a discrete component and it seems like the MSP430 isn't able to go high when connected to the MOSFET gate. If I leave the MOSFET disconnected it has no problem. But with the gate connected to the MOSFET it just will not go high. Not sure why this could be. I'm using NTD4963N MOSFET and this circuit configuration (but with a 47 ohm Gate Resistor and a 33k ohm pull down resistor from gate to ground).

Hi Nick,

That's really odd.  Any chance you accidentally swapped G and D?  That would give you exactly the results you are observing.

Also just to be sure - you are powering the MSP430 with 3.3V, not 5V as shown in the diagram, right?

Jeff

Nick Sorenson said:

I'm using NTD4963N MOSFET and this circuit configuration (but with a 47 ohm Gate Resistor and a 33k ohm pull down resistor from gate to ground).

the NTD4963N MOSFET is designed for 5V gate drive. You need a lower gate rated part. A partial gate drive could cause 0.4A * 6V = 2.4W heating.

There is a possibility that the transistor is fried and internally shorted. A quick voltage reading across the 47 ohm gate resistor will confirm this.

Even with 3V gate rated parts you may need to create undervoltage lockout monitoring. If supply is below 3V don't activate outputs.

For testing purposes use only a LED load until basic operation is verified .

Peter

Try

Hi,

Can I get the schematic of this solenoid drive.

Regards

Manoj

Just like Peter said, look at the VGs chart and you see that at 3.3v it's on but just barely.
It will create heat in this regions and will never fully supply the current you need.

A simple 74HCTxxx buffer will help you, or use a gate driver.
Gate drivers normally is only used for rapid switching as they can supply and discharge up to 1A to/from the mosfet's gate field.

Or use a mosfet that is fully on at 3.3v

Manoj R94504 said:

Can I get the schematic of this solenoid drive.

 Hi Manoj and Toni too, have you seen date of last post replying to?

Sun, May 20 2012 2:48 PM