[1000mp] MPV Driving SB220

[Bill Gode, Sr.]

Snubbing Diode (From Wikipedia):

When the current flowing is dc, another often seen form of a snubber is 
a simple rectifier diode placed in a circuit in parallel with an 
inductive load (such as a relay coil or electric motor). The diode is 
installed in the direction that ordinarily does not allow it to conduct. 
When current to the inductive load is rapidly interrupted, a large 
voltage spike would be produced in the reverse direction (as the 
inductor attempts to keep current flowing in the circuit). This spike is 
known as an "inductive kick". Placing the snubber diode in inverse 
parallel with the inductive load allows the current from the inductor to 
flow through the diode rather than through the switching element, 
dissipating the energy stored in the inductive load in the series 
resistance of the inductor and the (usually much smaller) resistance of 
the diode (over-voltage protection). One disadvantage of simple 
rectifier diode used as a snubber is that because the diode allows 
current to keep flowing, the relay may stay picked-up slightly longer; 
some circuit designs must account for this delay in the dropping-out of 
the relay.

73,

Bill, W9NHQ


----- Original Message ----- 
From: "Jan Erik Holm" <sm2ekm at telia.com>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
Sent: Tuesday, October 24, 2006 8:34 AM
Subject: Re: [1000mp] MPV Driving SB220


> What is a snubbing diode? I have never heard that
> expression before.
>
> /Jim SM2EKM
> ---------------------------
> Pete Smith wrote:
>> You can also play safe by putting a 220-ohm resistor in series with 
>> the switching lead to limit the current through the relay contacts; 
>> that device was published in QST many years ago, when relays in 
>> TS-930s like mine were being fried by the relay current - the stock 
>> SB-220 relay has no snubbing diode, which may be part or all of the 
>> problem.
>>
>> 73, Pete