What mosfet or solution could i use to act it like a relay switch? i guess something like a logic mosfet but im not sure its my first time working with mosfets or maybe do you guys have another solution?
To switch what, and what current?
A logic level MOSFET is the usual solution here. An N-channel MOSFET can switch the low side of the load. A P-channel MOSFET can switch the high side of the load, but needs an additional transistor to switch the gate. Switch the low side if you can to avoid that (N-channel MOSFETs are also cheaper for given specs compared to P-channel ones - the manufacturing process is easier)
Diagrams of using a MOSFET as a switch are all over the internet; I won't repeat those instructions here. Make sure that the MOSFET you select is logic level - if you're using a 3.3v microcontroller, you need a MOSFET that is rated to turn on at 3.3v (many logic level MOSFETs need 5v on the gate (spec'ed at 4.5v)).
The IRF3708 is a good default high power N-channel MOSFET - they're a little pricey, but their voltage and current ratings are sufficient for most hobby applications. For low current, there are a bunch of options. If the current is a couple of amps, there are some amazing options in small surface mount packages (I sell some of them mounted on breakout boards with a pulldown resistor, in my tindie store here)
DrAzzy:
if you're using a 3.3v microcontroller, you need a MOSFET that is rated to turn on at 3.3v
Not so well described.
People tend to see the "turn on" voltage in the datasheet which is very unhelpful. What you need to look at is the voltage or voltages for which the drain-source resistance (i.e., the lowest resistance) is specified.
AGames2911:
What mosfet or solution could i use to act it like a relay switch? i guess something like a logic mosfet but im not sure its my first time working with mosfets or maybe do you guys have another solution?
But, guys, as jremington stated, we really need more info from the OP before we can even begin to properly answer this question. For instance, the OP stated he/she wants something solid-state that will behave like a "relay switch", which encompasses both AC & DC. And if it's AC, then a mere MOSFET is not the answer.
The best solution I can offer, with the scant information provided is look into SolidState relays.
Or, even better would be if the OP read the following, so they have a better idea of how to help us help them:
How To Use This Forum
So bassicly im trying to let a e36 m3 dashboard work it needs 12v DC for the indicator lights. so i thought using a microcontroller to program those lights but a arduino has a max of 5v through the pins so thats why i thought a relay can come in handy but also mosfets. the current is max 30ma so its not that much.
and like DrAzzy said i personally think that is the logical solution for this. but do you guys think the same?
That's an easy use case for MOSFETs - you can use small, cheap logic level MOSFETs for that. Since you have a lot of them, it sounds like, it might be more convenient to use a multi-channel driver chip, The TBD62083 is a great option; with only 12v and the low current involved, even the very old BJT version (which is a worse switch - it drops like 1.3v across the switch, and gets hotter under load as a result), the cheaper ULN2803, will be fine. Those are the 8-channel versions; there's also a 7-channel one, TBD62003/ULN2003.
There are also parts like the TPIC6C595, which is a 595-style shift register with integrated MOSFET switches, so it can drive up to 100mA loads while being controlled over SPI like a 595 shift register, so you can control a great many outputs with just a few pins (you can chain them).
There are also TPIC6B595 and TPIC6A595 - with current limits of 150mA and 350mA per channel, and correspondingly higher price.
Paul__B:
Not so well described.People tend to see the "turn on" voltage in the datasheet which is very unhelpful. What you need to look at is the voltage or voltages for which the drain-source resistance (i.e., the lowest resistance) is specified.
Sorry, I was just getting sick of writing out the same description of what that meant. Forgot that people mistake Vgs(threshold) for the voltage needed to actually turn it on (the lowest Vgs for which Rds(on) is specified)
For 30mA loads a bunch of TO92 switching transistors like 2N2222's is more convenient.
Hi,
Have you got a schematic of the BMW e36 m3 instrument cluster?
Thanks.. Tom... 