MOSFET for reverse polarity protection

Stompboxes circuits published in magazines, books or on DIY electronics websites.

MOSFET for reverse polarity protection

Postby POTL » 16 Jun 2018, 00:53

Hello everybody.
Once again I decided to take an interest in protection from reverse polarity.
In classic pedals we have 2 popular protection options.
1) 1N4001 at which we lose tension
2) 1N4148 which works like a kamikaze
Both options are popular, but have the disadvantages described above.
Tell me more about the p-channel mosfet.
I understand correctly that it does not burn like 1N4148 and does not make voltage drop like 1N4001?
There are many variants of these transistors, what characteristics should I look at?
Image
Image

I looked at the Walrus boards and saw the components in the body of the sot-223.
Other elements capable of protecting the circuitry I did not see on the board.
What do you think - is this a mosfet?
If so, I have 2 questions:
1) What are the variants of schemes?
2) What parameters are important for a transistor?
POTL
Resistor Ronker
 
Posts: 275
Joined: 26 Sep 2016, 04:11
Has thanked: 64 times
Have thanks: 54 times

Re: MOSFET for reverse polarity protection

Postby marshmellow » 16 Jun 2018, 01:34

Read here first: http://www.geofex.com/Article_Folders/m ... switch.htm

You want low Rds_on and need to watch the current/max power dissipation specs. The power can be calculated with the Rds and the current drawn by the effect. Although in reality this is probably only of theoretical interest considering how little current the usual DIY builds require. The on-resistance and the current also determine how much voltage is dropped across the FET.

I've been using THIS ONE for years. It's small, cheap and won't have any problems with pretty much all effects (are there digital effects that draw more than half an amp? I don't know).

Some possible throughhole parts (Rds_on from bigger to smaller, price inversely):
- VP2106
- VP0106
- IRF9014

For this message the author marshmellow has received thanks:
POTL (16 Jun 2018, 04:45)
marshmellow
Resistor Ronker
 
Posts: 435
Joined: 16 Aug 2007, 08:31
Location: Germany
Has thanked: 13 times
Have thanks: 115 times

Re: MOSFET for reverse polarity protection

Postby POTL » 16 Jun 2018, 04:48

marshmellow wrote:Read here first: http://www.geofex.com/Article_Folders/m ... switch.htm

You want low Rds_on and need to watch the current/max power dissipation specs. The power can be calculated with the Rds and the current drawn by the effect. Although in reality this is probably only of theoretical interest considering how little current the usual DIY builds require. The on-resistance and the current also determine how much voltage is dropped across the FET.

I've been using THIS ONE for years. It's small, cheap and won't have any problems with pretty much all effects (are there digital effects that draw more than half an amp? I don't know).

Some possible throughhole parts (Rds_on from bigger to smaller, price inversely):
- VP2106
- VP0106
- IRF9014



Thank you! IRLML5103 is available in my country and the price is really attractive.
POTL
Resistor Ronker
 
Posts: 275
Joined: 26 Sep 2016, 04:11
Has thanked: 64 times
Have thanks: 54 times

Re: MOSFET for reverse polarity protection

Postby POTL » 16 Jun 2018, 05:26

I read the article, but I'm not sure, except for Rds you have to look at other characteristics?
For example volts and amperes or something else?

The Internet offers various variations of the scheme, in the article geofex it is said only about the addition of a resistor between the ground and the gate.
POTL
Resistor Ronker
 
Posts: 275
Joined: 26 Sep 2016, 04:11
Has thanked: 64 times
Have thanks: 54 times


Return to DIY Stompbox designs

Who is online

Users browsing this forum: No registered users and 1 guest