Mosfet Module Question

http://www.ebay.com/itm/Four-Channel-4-Route-MOSFET-Button-IRF540-V2-0-MOSFET-Switch-Module-For-Arduino-/171915397754?hash=item2806f4ca7a

Just to check this module claims to be made for the arduino, IRF540 datasheet states vgs = 10v, will modules like these fully turn on any load with 5v gate voltage?

I also noticed there is an optocoupler on the module, could I also ask if pwm will work on optocouplers?

From the listing:
"However, it is suggested that the controlled DC voltage is more than 9V."

So they may be deriving the gate drive from the voltage on the connector labelled "power". I wouldn't buy it without a look at the schematic.

By optocoupler, do you mean the 16 pin chip? How do you know it is an opto? I find it hard to read the printing on the IC.

Yes, Arduino PWM should work with optocouplers. Why not unless bandwidth considerations prevent it? What is PWM other than a digital pulse train?

Thanks aarg,

"In some extreme cases,It can be used to control 100V/33A DC circuit. However, it is suggested that the controlled DC voltage is more than 9V." - Ok, because initially I thought "controlled DC voltage" they actually meant the actual input gate voltage for each gate.

So if they are deriving the voltage from the "power" connector, does that mean that the mosfet gate can accept more than 10v, even if vgs=10v?

I searched for other sellers selling the same product with better pictures, I can make out the text on the chip, which is p52801-4.

Byork:
So if they are deriving the voltage from the "power" connector, does that mean that the mosfet gate can accept more than 10v, even if vgs=10v?

You are misinterpreting the datasheet. The part you see is the spec for Rds(on) which is measured when Vgs=10V. The gate-source threshold voltage Vgs(th) is 2.0V min and 4.0V max. The maximum gate-source voltage is +/-20V.

Maximum drain current when Vgs=5V is about 10A. So its possible the gate is driven with 5V.

It's unlikely that the p52801-4 is an opto, but possible.

The MOSFET is intended for use at 10v on the gate, and performs poorly at 4.5-5v (you really shouldn't assume 5v on gate if chip is running on "5v", particularly if you're PWMing it - that's why logic level fets are always spec'ed at 4.5v not 5v), see figure 1 on page 3 of the datasheet.

Dishonest and/or incompetent vendors like to sell 10v mosfet boards as if they are appropriate to control directly from an Arduino board; they are not. They will "sorta work" with light loads - far below their headline specs. Use a logic level MOSFET if the application is at all demanding.

As it happens, I sell MOSFET breakout boards in my Tindie shop (both bare boards and assembled with logic level MOSFETs)

Thanks aarg, DrAzzy, knew it was too good to be true. Mosfet breakout boards are exactly what I need, I have considered using prototyping boards, but the soldered connecting wires are just too messy. I will have a look at your products too, thanks again.

After doing further research, I have found that the mosfets themselves are actually switched on/off by the optocoupler, which is controlled by the arduino pins. The gate voltage of the mosfet is indeed sourced from the power input like aarg mentioned, not the pin inputs, which can then saturate the gate if >=10v. Some of the item listings I have found after, the recommended input voltage of the power terminal is 10v-100v.

But this raises another question, if the gate and the load are sharing the same power source, I would think the module should then only support up to the max gate voltage which is 20v without frying the mosfet. But these products are claiming to support up to 100v, and I don't seem to be seeing anything that appears to be limiting the voltage on the gate.

I would say that these modules should work with the arduino logic, provided the input voltage for the power terminal don't exceed the max gate voltage of the mosfet, which is 20v.

The chip on the board is indeed an optocoupler datasheet

BUT! The board is not isolated in ay way. Input- and output-ground are joined. The only reason that the optocoupler is used is to drive the gate of the MOSFET, so 5V should be fine.

// Per.

Zapro:
The chip on the board is indeed an optocoupler datasheet

BUT! The board is not isolated in ay way. Input- and output-ground are joined. The only reason that the optocoupler is used is to drive the gate of the MOSFET, so 5V should be fine.

// Per.

You are absolutely correct Zapro. The grounds are and required to be connected, and seems that the reason you have given is the only valid one for its usage.

Check out the Logic Level Mosfets from Sparkfun