Combined module Soft Start (inrush current limiter) & DC Blocker (trap, filter) – assembled and tested PCB

Fully populated and tested Soft start & DC Blocker/Filter/Trap combined module.

 80.00  74.00

  • USD: 88.41$

Sometimes a module for soft starting the big toroidal transformer (limiting the inrush current) along with blocking the DC component in the Mains is needed. And here is offered a combined Soft Start & DC Blocker module.

Basically it is a combination of two other my designs: soft start module ( and DC Blocker ( In deep description of both modules can be find in its corresponding pages. A simplified block-schematic can be seen on the pictures.

– AC mains working voltage: 230V or 120V (or some other one by demand)
– time delay for relay engagement: 3.5 sec.
– possibility to work with wide variety of toroidal transformers: 300 – 3000 VA
– current consumption with relay turned on ~ 100 mA

PCB for the schematic is with dimensions 110×110 mm.
PCB thickness: FR4 2.0 mm. Copper thickness: 70um (2oz). Surface finish – Nickel Gold (ENIG).
It is one-layer design with solder mask coating on both layers for best durability. Silk screen with parts layout is placed on the top of the PCB.

Schematic is designed to work with either 230V (European) or 120V (United States) AC mains. This is done by changing the capacitive divider’s value. If there’s need for work with different AC Mains voltage this can be calculated on request and tested with Variac.

Soft start part of the module utilizes a 20A power Omron G4A-1A-E relay. DC Blocker uses large 33000uf electrolytic capacitors. The overall power that module can handle is approx. 3000VA.

On the pictures you can see a bare PCB as well as fully populated one.

Note: Since the capacitive divider value and the value of resistor in series with transformer’s primary winding depend on the AC mains voltage applied to schematic, let me know your variant – 230V or 120V AC. In case the AC mains voltage in your country is different than the noted above, let me know and the optimal value for capacitor will be find.
PCB is populated with all possible paralleled resistors (7 pcs.) which form the series resistor. This corresponds to the max. handled transformer power (approx. 3000 VA). In case your transformer is smaller than the mentioned above, contact me prior to purchase and the optimal resistor’s value will be picked up. Otherwise you will get the full resistors set and could tune it’s value by un-soldering (cutting) unneeded ones.

On the PCB are placed 3-pins connector for AC Mains input and AC Output connector with ability for attaching up to 3 consumers with independent Live, Neutral and Ground terminals.

Weight 0.5 kg