Quad DC switch design for 20 Amps and 500 Volts (DC)

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Physical Product


Personal Use

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Quad 20 Amp, 500 V DC low-side switch (Resale rights)
$30.00
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Quad DC Low-Side Switch in our testing jig

Quad DC Low-Side Switch in our testing jig

Control lights, motors, heaters, etc…

Want to build a robot? Want to build a robot with big motors?

We do!!

DC control switches are very useful for a wide range of applications (if properly designed). To power a big inductive load (motor) the circuit must incorporate reverse spike protection and you must plan for heat dissipation.

Quad MOSFET Switch Backside Control Circuit

Quad MOSFET Switch Backside Control Circuit

Our design uses high grade Power MOSFETS (N-MOS) to create 4 separate switches all fed from the same power rails. We have incorporated “over designed” reverse spike protection and have big heat sinks mounted to each switch.

We didn’t want to sacrifice switching speed (Pulse Width Modulation is our favorite method to dim lights, change motor speed, implement temperature controlled environments, etc…..) for convenience so we used FAST power MOSFETS and then added a MOSFET driver circuit so that you may easily connect your micro-controller or embedded CPU without having to design voltage level shifters.

Top-Down view of the Quad DC "low-side" switch

Top-Down view of the Quad DC “low-side” switch

We routinely use these switches with 24V (DC) power supplies to drive high temp ceramic heaters, thermoelectric coolers, LED strings and uni-directional DC motors (fans & DC pumps).

These DC switches are “low-side” switches: Placed between ground and the load to be driven.

We are designing high-side switches using PMOS power MOSFET switches. We originally thought “low-side” switches would cover all of our needs: then we encountered a situation which proved us wrong (which is why we love designing: we are able to learn & learn…)

We are also designing a high current controller for bi-directional motor usage (a “connection variation” of our current design).

The half-pipe 3D design was developed so that in extreme usage scenarios a single (big) fan may be used to vent excessive heat. The half-pipe allows us to put two of these units back to back and gang 8 switches.

Hand Crafted in Colorado:

3D Print for the Quad DC Switch

3D Print for the Quad DC Switch

Printing the structure is fast (for a 3D printer): Assembly of the electrical circuit requires about 40 hours of labor. There are currently no automated assembly machines for 3D Printed Circuit Boards (Opportunity knocking?).

Construction is not difficult: no harsh chemicals, no “photo-lithography”, no expensive “conductive filament” to jam your extruders: We use thick 2 mil copper tape and a X-acto knife to create the traces and then the task becomes a normal “insert components & solder” process.

Quad DC Switch with Copper applied

Quad DC Switch with Copper applied

Tip: Use a good solder flux (Soldering needs to be quick or you will melt the 3D printed structure under the copper traces.)

Tested:

We don’t have the necessary equipment to test the Quad DC switch at it’s maximum ratings (We don’t have a 500 Volt 80 amp {20 Amps X four switches} power supply)

We have tested each switch at 24V and 15 Amps: We have that power supply. The circuit gets hot but works flawlessly (a fan solved the heat dissipation challenge )

Single low-side DC Switch prototypes

Single low-side DC Switch prototypes

We didn’t start out by designing a Quad DC switch: We started with one switch…. Tested it extensively, worked through 5 or 6 different physical designs before we converged on a design that was excellent at dissipating heat.

While the circuit and components are designed for and rated to handle 500 Volts and 20 Amps per circuit we recommend caution when exceeding 500 Watts per switch ( 2000 Watts per unit ).

We would be happy to work with customers who require higher wattage usage to validate the design for their specific requirements. We would recommend some “system design consulting” to implement switch temperature sensing and fan speed control (… And someone needs to purchase or build an expensive power supply….)

Quad DC Switch with components installed

Quad DC Switch with components installed

Our original requirement was 2 Amps per switch at 24 Volts ( ~50 Watts per switch, 200 Watts total )….. So we massively over-designed to meet our requirements to minimize energy wasted as heat and provide a long service lifetime. Works great! ( We met our requirements completely)

We have also tested these switches with high voltage LED driver power supplies (Over 200 Volts but only a couple of Amps of current => We operated at approximately 500 Watts of power per switch ). The circuit was warm but not hot (We used PWM and never exceeded 90% on)

We designed the circuit connections (traces) to support the full load: doubling and tripling trace thickness as necessary to limit temperature rise through the conductor.

CAUTION: The engineering maxim: “If you haven’t tested it => It doesn’t work” should be your guidance.

Usage Notes:

Quad DC Switch driving 4 ceramic heaters

Quad DC Switch driving 4 ceramic heaters

Power MOSFET DC switches are high efficiency devices IF the MOSFET is turned “completely on”. “A little on” will burn the MOSFET…. “Poof… No more switch”.

In a typical micro-controller system you will have your micro-controller voltage (5V or 3.5 V) and your heater / fan / Led / thermoelectric cooler voltage (we use 24 V) and you will also need a “MOSFET turn-on Voltage”: 10 – 12 Volts (we use 12 V). We mostly use 24V power supplies which we complement with low-cost (EBay) buck converters to create the other voltages we need.

You may notice that our Quad switch doesn’t have enough “connectors”: We provide a 6 pin in-line connector to route the 4 switch control signals and the power and ground for the “MOSFET turn-on Voltage”…. We have no connectors for the primary fan / heater / LED Voltage. This isn’t a design error:

We realized that placing “main power in” connectors on the switch assembly would limit “usage”. A good connection location for one design implementation was a “bad” location for another implementation.

Normally, sub-system designers don’t have any choice: They have to put the connectors somewhere. In the 3D printing mechanical / electrical co-existence world these “must place” limitations disappear: We put the power connector on the switch “mount” and then the mount passes the power to the Quad switch. Mounts are fast to print and easy to complete with electrical paths (30 minutes). This allows us to design “implementation specific” mounts and a “general use” Quad DC switch.

We provide an additional “testing mount” with main power connectors when you purchase our physical product ( and we would be happy to create a “design specific” mount for your implementation: Contact us for a quote => You get the “friends and family” discount when you purchase our physical product: It is ridiculously expensive. )

The Load Connectors have a similar design philosophy (not designed into the main Quad Switch). For our physical products we include (and solder on) a load “top plate”. If you would prefer we will include the top plate load connectors but NOT solder the plate in place. Soldering the top plate requires a little skill with a soldering iron to avoid melting the connection tabs. We developed that skill through trial & error: which is why we decided to solder the top plate in place unless we are requested “not to”….

Zombie Apocalypse survival necessity:

Zombie_Apocalypse_Warning_SignHigh power DC switches are a necessity for survival “post apocalypse”. All forms of alternate power generators (wind, solar, thermal, etc…) benefit when the energy is used efficiently => PWM through a power MOSFET is how to increase energy usage “efficiency”.

While our physical product is ridiculously expensive our 3D models are dirt cheap.

Learning how to construct your own 3D printed “circuits” is a critical survival skill. We include “construction instructions” in addition to the 3D model (and a components parts list using Digi-Key part numbers => American company based in norther Minnesota that stocks high quality electronic components). Anyone could built this circuit if they are a little patient and have fine motor control skills (Soldering “little things” requires both).

Earth Friendly:

We print our Quad DC Switch (Physical product) using PLA filament that is derived from corn husks and decomposes when exposed to sun light.

High Resolution 3D Model:

Its not obvious to everyone that if you use a low resolution 3D Model the “resolution of your 3D Printer” doesn’t matter. We sell only high resolution 3D Models to produce professional quality printed objects. High Resolution 3D models take longer to “slice” into 3D Printer commands but they only take a few seconds longer to actually print.

Intellectual Property Rights include:

When you purchase Intellectual Property Rights you are given the high-resolution 3D model, the original 3D parametric design source model, a bill of materials and 20 hours of consulting time.

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