I have a PIR sensor that outputs 3.7v when active. it is powered by a 6v battery. I am trying to run flashing LED's (built in resistors) off 6v battery as well when the PIR sensor is high at 3.7v. is the IRF510 gate capable of being switched at 3.7v from the PIR sensor? also what else do I need to hook this up and how? The reason want the lights triggered with 6v rather than 3.7v is because they are too dim under 3.7v

Thanks in advance

 

is the IRF510 gate capable of being switched at 3.7v

No, its maximum gate threshold voltage is 4v.
You need a logic-level type MOSFET where the ON resistance, Rds(on) is specified at a Vgs of 3.5V or less on the data sheet.

 

Could you please suggest a mosfet?

 

Maybe you could add a CD40109 between the PIR and the mosfet, it's a level (voltage) shifter made for things like this.
http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=cd40109b-q1&fileType=pdf

 

I have a PIR sensor that outputs 3.7v when active. it is powered by a 6v battery. I am trying to run flashing LED's (built in resistors) off 6v battery as well when the PIR sensor is high at 3.7v. is the IRF510 gate capable of being switched at 3.7v from the PIR sensor? also what else do I need to hook this up and how? The reason want the lights triggered with 6v rather than 3.7v is because they are too dim under 3.7v

Thanks in advance

Are your LEDs made to run on 6 volts?

 

Are your LEDs made to run on 6 volts?

Yes!

 

Could you please suggest a mosfet?

If you tell me where you are located and can buy electronic parts I can give you a better suggestion.

 

If you tell me where you are located and can buy electronic parts I can give you a better suggestion.

Elmira, NY. the only place I know for with electronics is radio Shack, thank you for all your help

 

This should work.

 

This should work.

Thank you, will order!

 

Hi Mike,

When you evaluate a MOSFET, look in the datasheet for the graph Vgs vs. Ids. This will tell you how much drain to source current can flow given a certain amount of gate voltage. In the datasheet that crutschow posted, this graph is in figure 8 (see attached). This shows that if you energize the gate with 3.7 volts, the MOSFET can sink ~15 Amps. So this one will work for you.

John

 

Thank you for the lesson!

Much appreciated

 

................
When you evaluate a MOSFET, look in the datasheet for the graph Vgs vs. Ids. This will tell you how much drain to source current can flow given a certain amount of gate voltage. In the datasheet that crutschow posted, this graph is in figure 8 (see attached). This shows that if you energize the gate with 3.7 volts, the MOSFET can sink ~15 Amps. So this one will work for you.

That graph shows the current for a Vds of 15V which is of marginal usefulness for characterizing the MOSFET as a switch.
Attached is a more pertinent graph.
It shows that at a Vgs of 3.7V and a drain current of 14A the nominal ON resistance is <100mΩ.
But note these are typical and not worst-case values.

 

is the IRF510 gate capable of being switched at 3.7v from the PIR sensor?

look at the datasheet - at that kind of Vgs, you can barely turn on the mosfet.

Try a bjt or a mosfet with lower Vgs at your desired current levels.

 

Crutschow, what was the origin of that Figure 9 that you showed? The IRF510 data sheet from Vishay is quite different, and shows what Dannyf said--in fact the "Typical transfer characteristics" graph doesn't even go below Vgs = 4V, and the curve is pretty close to zero at that point. The data sheet also lists a maximum continuous current of 5.6A.

See Figure 3 here: http://www.mouser.com/ds/2/427/sihf510-105610.pdf

Oh, now I see in the Saturday 12:04 post, that's not the IRF510. That explains it!

 

Crutschow, what was the origin of that Figure 9 that you showed?

It's this data sheet for the RFD14N05L.

 

FQP30N06L, would this work?

 

FQP30N06L, would this work?

Yes, that should work.

 

So I set this up with the mosfet listed above, however the mosfet appears to be latching. the negative drain and source stay connected after the gate voltage drops to zero.

 

So I set this up with the mosfet listed above, however the mosfet appears to be latching. the negative drain and source stay connected after the gate voltage drops to zero.

What do you mean "negative drain"?
The drain voltage must be positive with respect to the source.
Post a schematic of your circuit.
Try connecting a 10kΩ resistor from the gate to source of the MOSFET.