Your choice of diode (IN4007) would also work, it is just physically bigger than a IN4001 (and has a higher voltage tolerance, probably *why *it's bigger). MOSFETs with a low RDSon do not require heatsinks!Īs it happens I don't think your TIP120 will either: 12v 120ma = 1.44W which it may be able to dissipate without further ado. The voltage drop across a fully switched on MOSFET is pretty minimal, although that 0.5 ohm one mentioned above is about the highest I've ever seen!Īs the resistance is greater in a transistor than in a MOSFET (OK, that too is a transistor but a special type) so the heat increases and hence the need for heatsinking. So some circuits would not perform as well (eg motors) if they have a large resistance transistor in series with them, as the voltage drop would be too much. But the resistance between collector and emitter would be higher than that of a logic level MOSFET. In general terms your TIP120 would work if all it was passing was 120mA. Why does the curve show a reading of about 6.5A at 10V instead of the 2A of RDSon? I just noticed there are two V values, the one on the x-axis and the iso-volt curves. Then I looked at the curves and saw this:Īnd thus I realized I didnt really understand these curves. So even though RDSon was 10V = 2A, I figured I might get about 1A at 5V. I was thinking, since its Vthreshold is 0.8V-2.4V, I could get a bit of mA out of it. I was looking at another arduino tutorial that uses a ZVN2110A, which is also not a logic level mosfet. I just have one doubt about mosfets and datasheets. It turns out I dont have an IRF510 anyway, what I do have is an IRLB-8721 which is great because it IS a LL mosfet. I also know that mosfets or transistors are meant to be used ON or OFF, but not gradually as I once thought I could get away with milking the IRF510 for the few mA it might produce at 5V at the Base. Turning over to the MOSFETs, I understand that IRF510 and IRF540 are not LL and so they dont have an RDSon for 4.5V. If my solenoid draws 194mA at 12VDC, why would the TIP120 not work, or would it? Im looking at the IC which is collector current and its stated as 5A. I guess I have seen many tutorials with Arduino about running solenoids with BJTs like the TIP120 because those solenoids used require very little current. What other parameters should I look out for with Diodes besides the VRRM? The values for each are:Ĥ148 - 100V - I also happen to have a 4148 so I guess I could use this one instead. The instructable calls for a 4004 but states a 4001 will do. The diode's most important parameter is the Peak Rep Reverse Voltage from what I gather. Its based on an instructable I found which used a BJT (TIP120) with a 1N4004 diode. I just tried reviewing the set up for a 12VDC/195mA solenoid valve I would be powering from a 12V lead acid battery. I believe that if I understand the parameters of these devices it will help me understand more clearly the differences of how they work. Here is LTSpice and what Id like to know is how to make an analysis where I ramp up the voltage from 0-5V at the gate such that I can study the V and A at different points in the circuit: So it was suggested I try to model it in LTSpice and iCircuit and Id like help making sure my setup is correct. But for now I want to get a clearer picture of what happens in the circuit with a MOSFET when I apply the gate voltage. I also would like to eventually use an optocoupler to separate the circuits just to be on the safe side. I wanted to start with anything I had available but quickly realized I need a Logic Level MOSFET and I need to carefully wire my circuit with a fuse for the lead acid battery (12V) powering the 12V/2.5A or 12V/350mA valve options I have. Ive seen about 10 videos on youtube which are quite helpdul and so far I understand I need to choose my MOSFET correctly. I thought I understood BJTs until I ran into MOSFETs. Im tyring to get into my first solenoid project and I started learning about mosfets.
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