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For switchong dc power on/off a solid state device such as mosfets (n-channel - sink, or p-channel - source) are better option than a relay, but they don't offer isolation option.
Also, one has to make sure that the Ron of a mosfet working as a switch is as low as possible, preferably <0.01Ω, in some cases ..
Regards,
IanP
When a mosfet is on, doesn't it produce heat which lower its efficiency?
i'm making an auto on switch for my scooter. A tilt switch will be connected to the mosfet which will connect the battery to the scooter (16v @ 8amp) when ever the steering bar is raised up. Is it a good idea to use a mosfet in my project?
Ron is internal serial resistance of mosfet's channel when it is ON. Just imagine situation that Ron ≈ 1Ω and the current is ≈5A. What you have is 5V accross D and S and 25W of heat is generated. Now take one with Ron ≈ 0.01Ω. In the latter case the voltage accross mosfet will be ≈0.05V and heat will be only 250mW ..
For your application I would use p-channel mosfet such as IRF5305 or similar ..
Here are some other examples of low-resistance p-channel mosfets:
IRF5210, MTP50P03HDL, RFG60P05E ...
So, if you don't have access to similar mosfets better use a relay ..
Regards,
IanP
If I use a relay, should there be some kind of protection circuit to protect the 555 timer chip from the relay? I use the 555 turn on the scooter for an x amount of time when ever the tilt switch trips.
As far as contact resistance is concerned, you may almost ignore it. Sme power will be used to activate a relay, and that depends on the relay's size and col resistance.
Usually, when you switch dc power with a relay you will have a "spike", which can be dangerous for electronic components, so you can consider basic protection to 555 power line (zener diode + cap) and/or inputs (again, a zener diode..).
Regards,
IanP
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