My Question is:

Is this a effecient way of filtering high voltage spikes?

If so is the way I drawn the circuit even correct...

How to size the components to work so that any vehicle high voltage spikes get filtered.


I have a pump controller circuit that will be powered by a 12v battery that is charged with a stator.

I need to protect from voltage spikes...

For more info look here: Circuit Board Design...Getting Rid Of A Relay and Adding a Choke and Capacitor Filter?

@Transistor mentioned possibly a choke and capacitor filter...

I've been reading up on this and the more I read the more confused I get.

Here is what I've come up with so far...

I don't know how to size the componets correctly and running a simulation didn't help me...


simulate this circuit – Schematic created using CircuitLab

Figure 1. Clumsy Voltage Filter


simulate this circuit

Figure 2. Pump Controller Circuit

  • \$\begingroup\$ Did you mean protect the automotive electronics? from spikes generated by pump switch from conducted noise or more likely it is radiated noise. If so which device is affected? The pump does not need protection from spikes, as it is the generator. \$\endgroup\$ Mar 28, 2019 at 21:24
  • \$\begingroup\$ No there are spikes generated from other solenoids valves on the vehicle before the pump circuit... \$\endgroup\$
    – Sam burris
    Mar 28, 2019 at 21:47
  • \$\begingroup\$ I have not tested this new circuit out as I am using a latching relay with diodes ect. Do I even need to put in a filter? @Sunnyskyguy EE75 \$\endgroup\$
    – Sam burris
    Mar 28, 2019 at 21:48
  • \$\begingroup\$ What is I1, it is unclear what you are trying to do, it also depends on what "circuit board" is. \$\endgroup\$
    – Voltage Spike
    Mar 28, 2019 at 21:52
  • \$\begingroup\$ l1 is supposed to be an Inductive choke... Updated my question \$\endgroup\$
    – Sam burris
    Mar 28, 2019 at 22:05

1 Answer 1


some thing like this, using the popular implementation of a filter ---- one series element and one shunt element


simulate this circuit – Schematic created using CircuitLab

We add the resistor to dampen. R == sqrt( L / C).

  • \$\begingroup\$ What is the heavy wire input/output do? @analogsystemsrf \$\endgroup\$
    – Sam burris
    Mar 29, 2019 at 15:51
  • \$\begingroup\$ build this filter over a square inch of Ground plane. And have both input wires on the left side; put both output wires on the right; notice the 3 groungs? Keep them far apart. \$\endgroup\$ Mar 30, 2019 at 3:01
  • \$\begingroup\$ As Someone who is not familiar to what you are talking about where would I go to read about what your talking about? @analogsystemsrf \$\endgroup\$
    – Sam burris
    Apr 1, 2019 at 19:44
  • \$\begingroup\$ this is a voltage divider: Vout = Vin * Zshunt / (Zshunt + Zseries). The use of a low-inductance capacitor (surface mount) and those small pieces of foil, has the purpose of making the SHUNT become as small as possible, thus the attenuation of high-frequency fast-rise-time trash will the best possible. \$\endgroup\$ Apr 6, 2019 at 4:30
  • \$\begingroup\$ scroll down to the end of this answer electronics.stackexchange.com/questions/295629/… and notice how GRIDS can be modeled in SPICE. Draw that 1cm by 6cm foil with about 5 by 30 squares; you will see very little interference gets to the RIGHT side; my hand computations show 12dB attenuation per square of distance. \$\endgroup\$ Apr 6, 2019 at 4:39

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