Question about JS0
05-07-2009, 01:21 PM
#2
Boost Pope
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,026
Total Cats: 6,592
JS0 itself is just a pin on the CPU. It is at +5 when active, and ground when inactive.
CPU pins, by themselves, are not able to source or sink very much current, however. In order to make it to anything useful, you'll need to connect a transistor to it, as is done with the relay driver modkit. If you use a PN2222 or similar, you'll then have an output which goes to ground when active.
CPU pins, by themselves, are not able to source or sink very much current, however. In order to make it to anything useful, you'll need to connect a transistor to it, as is done with the relay driver modkit. If you use a PN2222 or similar, you'll then have an output which goes to ground when active.
Reply
0
0
05-07-2009, 03:33 PM
#4
Elite Member
iTrader: (1)
Join Date: Jun 2006
Location: Warrington/Birmingham
Posts: 2,642
Total Cats: 42
For the latter you just need a simple transistor circuit as Joe describes. For the former you need to build the WI circuit as described in the Megamanual
Reply
0
0
05-07-2009, 03:49 PM
#5
Boost Czar
iTrader: (62)
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,493
Total Cats: 4,080
Reply
0
0
05-18-2009, 05:46 PM
#6
Elite Member
Thread Starter
iTrader: (12)
Join Date: Jan 2007
Location: Hermosa Beach, CA
Posts: 2,573
Total Cats: 12
I dont get it, to me it seems the diode is the wrong way, when the transistor opens, it will alow current to pass the relay and flow through the diode? Shouldent the diode be the other way?
Reply
0
0
05-18-2009, 08:48 PM
#7
Boost Pope
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,026
Total Cats: 6,592
When an inductive device which has been passing DC is shut off, the electromagnetic field within it collapses back into the winding, inducing a large voltage spike in the reverse direction. In the case of an ignition coil, this is a good thing as it drives the spark plug. In the case of a solenoid or a relay, this is generally undesirable.
The diode is there to provide a bypass across the device, to essentially short-circuit this spike and prevent it from propagating outwards.
The diode is there to provide a bypass across the device, to essentially short-circuit this spike and prevent it from propagating outwards.
Reply
0
0
05-18-2009, 11:05 PM
#8
Elite Member
Thread Starter
iTrader: (12)
Join Date: Jan 2007
Location: Hermosa Beach, CA
Posts: 2,573
Total Cats: 12
When an inductive device which has been passing DC is shut off, the electromagnetic field within it collapses back into the winding, inducing a large voltage spike in the reverse direction. In the case of an ignition coil, this is a good thing as it drives the spark plug. In the case of a solenoid or a relay, this is generally undesirable.
The diode is there to provide a bypass across the device, to essentially short-circuit this spike and prevent it from propagating outwards.
The diode is there to provide a bypass across the device, to essentially short-circuit this spike and prevent it from propagating outwards.
Reply
0
0
Thread
Thread Starter
Forum
Replies
Last Post
bigmackloud
Miata parts for sale/trade
19
01-08-2021 11:24 AM
JesseTheNoob
DIY Turbo Discussion
15
09-30-2015 02:44 PM
