Diode snubber ?
curious1
Posts: 104
Below is clip from wiki. I have a small 24vdc 2a mech. PLC type·relay controlling a coil in a pneumatic valve·that arcs once in a while and I'd like to protect the contacts with a diode. What is the formula or how do you determine what diode to use ?
Thanks,
RC
[noparse]/noparse][url=http://en.wikipedia.org/w/index.php?title=Snubber&action=edit§ion=2][b][u][color=#0000ff]edit[/color][/u][/b][/url Diode snubbers
When the current flowing is DC, a simple rectifier diode is often employed as another form of snubber. The snubber diode is wired in parallel with an inductive load (such as a relay coil or electric motor). The diode is installed so that it does not conduct under normal conditions. 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 over 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 the diode allows current to continue flowing. This may result in the relay remaining picked-up slightly longer; some circuit designs must account for this delay in the dropping-out of the relay.
Post Edited (curious1) : 4/25/2007 10:06:17 PM GMT
Thanks,
RC
[noparse]/noparse][url=http://en.wikipedia.org/w/index.php?title=Snubber&action=edit§ion=2][b][u][color=#0000ff]edit[/color][/u][/b][/url Diode snubbers
When the current flowing is DC, a simple rectifier diode is often employed as another form of snubber. The snubber diode is wired in parallel with an inductive load (such as a relay coil or electric motor). The diode is installed so that it does not conduct under normal conditions. 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 over 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 the diode allows current to continue flowing. This may result in the relay remaining picked-up slightly longer; some circuit designs must account for this delay in the dropping-out of the relay.
Post Edited (curious1) : 4/25/2007 10:06:17 PM GMT
Comments
Looks like these will do the trick. Cheap too, $1.99 for 100 of them.
Thanks again Mike.
P/N: 1N4002
Similiar to 1N4001, but higher PIV
30A Surge Current
1A Continious Current
0.8V Max Voltage Drop
Great for general purpose rectification