| |
EB2DVY > PSK31 25.01.00 00:03l 80 Lines 2522 Bytes #-9680 (0) @ WW.SYD.NSW.A
BID : 850-EB2DVY
Read: OE1RRB GUEST
Subj: PSK31 Digest V1 #291
Path: OE1XAB<OE3XPR<OM0PBM<OM0PBC<OK0PHL<OK0PRG<OK0POK<9A0YRB<PP5BLU<WU3V<
EA7URC<EA7GRA<EA5URD<EA5RKE<EA5RCI<EA5VDR<EA2BBS<EA2K<EA1URR<EA1URM<
EA2RCF<EA2G<EA2URV
Sent: 000123/2210Z @:EA2URV.EABI.ESP.EU #:38324 [URV-ABRA Bilbao] $:850-EB2DVY
From: EB2DVY@EA2URV.EABI.ESP.EU
To : PSK31@WW.SYD.NSW.AUS.OC
De: Psk31 Digest <owner-psk31@aintel.bi.ehu.es>
Para: <psk31-digest@bipt106.bi.ehu.es>
Asunto: Psk31 Digest V1 #291
Fecha: martes 18 de enero de 2000 4:19
Psk31 Digest Tuesday, January 18 2000 Volume 01 : Number 291
In this issue:
RE: [psk31] having a tough time: FIXED!
Re: [psk31] having a tough time: FIXED!
[psk31] RE RELAY COILS:
See the end of the digest for information about psk31-digest
----------------------------------------------------------------------
Date: Mon, 17 Jan 2000 11:05:23 -0500
From: Richard Carter <rcarter@isi.com>
Subject: RE: [psk31] having a tough time: FIXED!
A relay coil is an inductor. When you turn off the relay, the inductor has
nowhere to discharge, so you will get a very large negative spike on the
serial control line.
Unless the circuit has a diode to clamp the output voltage, the output
transistor will blow. You will have this problem even if you use an external
transistor to energize the relay.
Rich Carter - KE1EV
- -----Original Message-----
From: Bob Lewis [SMTP:aa4pb@erols.com]
Sent: Thursday, January 13, 2000 5:06 PM
To: Greg Heath; psk31@bipt106.bi.ehu.es
Subject: Re: [psk31] having a tough time: FIXED!
Unless you've got a very low current relay, you're
risking cooking the serial port.
------------------------------
Date: Mon, 17 Jan 2000 12:51:35 -0500
From: "Bob Lewis" <aa4pb@erols.com>
Subject: Re: [psk31] having a tough time: FIXED!
A very good point. Depending upon the inductance
of the relay coil and the breakdown voltage rating
of the transistor it may fail shorted. Any time
you control a DC relay with a solid state device
you should have a reverse connected diode
(connected such that normal current flow is
through the coil rather than the diode) across the
relay coil. Even if you control the DC relay with
a manual switch, you should use a diode to prevent
possible arcing of the switch contacts.
------------------------------
Date: Mon, 17 Jan 2000 13:40:16 EST
From: JSchell447@aol.com
Subject: [psk31] RE RELAY COILS:
One more point on the subject of inductive kick from rapid shut off of the
current driving the relay coil, is that damage can also occur to the coil
itself. The winding of the coil is usually insulated with an enamel coating.
The high voltage may break down this insulation causing shorted turns.
Jim W4HAS...
------------------------------
End of Psk31 Digest V1 #291
***************************
Read previous mail | Read next mail
| |
