SoCalMacDude
New Member
Need snubber circuit to protect the logic components.
I'm using a DTMF Decoder kit from Ramsey Electronics
( h**p://www.ramseyelectronics.com/cgi-bin/c...=action&key=TT7 )
to sense touch tones from an audio channel. I used it to drive relays to trigger pneumatic solenoid valves, for a halloween project! Apparently the EMF from the coil turning off was blowing the big chip in the kit.
I have a new circuit design, replacing the mechanical relays with optoisolators triggering solid state circuitry (FET) to power the coils. When the TT7 kit's DTMF decoder 5V output pin goes low, the signal is sent through a 30ft. Cat5 cable to the optoisolater, which triggers the IRF830 MOSFET.
My question is that I am concerned that the snubber circuit in this schematic may not be enough to protect everything. I was reading that a good strategy is to channel the energy to a capacitor, then discharge it through a resistor.
I'm not sure how to do that, or if it is best, or what values of components would work.
Can anyone draw in an effective snubber circuit for me?
I will use one of these circuits for each item controlled, and one device I need to control is a 24V coil. The FET has a max gate voltage of ±20V, and with the 24V supply, I'm afraid it will blow. How can I drop that voltage to the gate?
Here's my current circuit design. Any help would be very much appreciated:
**broken link removed**
I'm using a DTMF Decoder kit from Ramsey Electronics
( h**p://www.ramseyelectronics.com/cgi-bin/c...=action&key=TT7 )
to sense touch tones from an audio channel. I used it to drive relays to trigger pneumatic solenoid valves, for a halloween project! Apparently the EMF from the coil turning off was blowing the big chip in the kit.
I have a new circuit design, replacing the mechanical relays with optoisolators triggering solid state circuitry (FET) to power the coils. When the TT7 kit's DTMF decoder 5V output pin goes low, the signal is sent through a 30ft. Cat5 cable to the optoisolater, which triggers the IRF830 MOSFET.
My question is that I am concerned that the snubber circuit in this schematic may not be enough to protect everything. I was reading that a good strategy is to channel the energy to a capacitor, then discharge it through a resistor.
I'm not sure how to do that, or if it is best, or what values of components would work.
Can anyone draw in an effective snubber circuit for me?
I will use one of these circuits for each item controlled, and one device I need to control is a 24V coil. The FET has a max gate voltage of ±20V, and with the 24V supply, I'm afraid it will blow. How can I drop that voltage to the gate?
Here's my current circuit design. Any help would be very much appreciated:
**broken link removed**
Last edited:
