Home
JAQForum Ver 20.06
Log In or Join  
Active Topics
Local Time 19:40 29 Mar 2024 Privacy Policy
Jump to

Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.

Forum Index : Microcontroller and PC projects : picoMite Mini

     Page 2 of 2    
Author Message
TheRockGod
Newbie

Joined: 01/04/2022
Location: Australia
Posts: 8
Posted: 08:24am 05 May 2022
Copy link to clipboard 
Print this post

Thanks all...I put my transistors in contrary to the silk screen...and they work!
  Of course, because mosfets will conducts in both directions...So, I assumed this to be correct.    I stand corrected.
  At any rate, the board works well...now I'm awaiting the expansion boards to arrive.

Many thanks for a great board design.

Tony
 
phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 1722
Posted: 12:20pm 05 May 2022
Copy link to clipboard 
Print this post

"I put my transistors in contrary to the silk screen...and they work!"

Could be risky. Most MOSFETS have a diode from drain to source. If the anode is on the 5V side the voltage on the Pico pins may be too high. Measure them to be sure.
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 5648
Posted: 01:33pm 05 May 2022
Copy link to clipboard 
Print this post

What looks to be a better substitute for the 2N7000 would be the VN10KN3-G, which has the same pinout but VGS(th) is 2.5V. It'll be less "borderline". The 2N7000 can be as high as 3V - it'll probably work most of the time.


Re. connections.
Now I don't know what to believe.
ST data sheet https://www.st.com/resource/en/datasheet/cd00005134.pdf
Labels pins 1-2-3 as Source-Gate-Drain
Same as Vishay https://www.vishay.com/docs/70226/70226.pdf
(who point out that BS170 is the reverse way round)
Microchip also agree https://ww1.microchip.com/downloads/aemDocuments/documents/APID/ProductDocuments/DataSheets/2N7000-N-Channel-Enhancement-Mode-Vertical-DMOS-FET-Data-Sheet-20005695A.pdf

ONsemi datasheet https://www.onsemi.com/pdf/datasheet/nds7002a-d.pdf
Labels pins 1-2-3 as Drain-Gate-Source

Looks like ONsemi have it wrong.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 1722
Posted: 12:38am 06 May 2022
Copy link to clipboard 
Print this post

"Now I don't know what to believe."

Safest thing is to measure D-S with multimeter diode range. No matter what the data sheets say you will then know for sure.

With the 2N7000s I have the left pin goes to the Pico and the right to the pullup / PS2 - Flat side facing you, legs pointing down.
.
Edited 2022-05-06 10:46 by phil99
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 5648
Posted: 07:32am 06 May 2022
Copy link to clipboard 
Print this post

That would be Source-Gate-Drain then. Sounds right.  :)
Edited 2022-05-06 17:32 by Mixtel90
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
     Page 2 of 2    
Print this page


To reply to this topic, you need to log in.

© JAQ Software 2024