Custom Transformers & Coils for Security, Detection & Sensing Systems

Security and detection equipment doesn’t get a second chance. An RFID coil at a controlled-access door, a current transformer monitoring critical electrical equipment, a trigger pulse transformer firing a fast-switching device in a detection circuit — the components inside must perform every cycle, every shift, for the operating life of the system.
Custom Coils USA designs and manufactures custom transformers, current and pulse transformers, antennas and air coils, and specialty pulse components for engineers building detection and sensing equipment where field reliability is the spec, not a target. We’re a VPI dry-type specialty shop, ISO 9001 certified, and USA-manufactured in Alcester, South Dakota since 1967.

Why the Right Component Changes Everything

In detection and sensing, the margin between a clean signal and a missed one often comes down to how precisely a transformer or coil was wound and whether it holds that precision after a year of duty cycling, thermal swings, and continuous operation. Detection systems run 24/7, see variable loads, and need to hold calibration in service, not just at initial test. Catalog parts, designed for the average case, don’t always survive that.

Our Products for the Security & Detection Industry

Trigger Pulse Transformers

Our trigger pulse transformers fire the gate of fast-switching devices  thyratrons, IGBTs, SCRs, MOSFETs used in laser-based intrusion detection, high-intensity strobe drivers, and similar pulse generation circuits. These applications demand precise pulse timing, controlled rise time, and consistent waveform shape across millions of cycles. We design the winding geometry, isolation system, and core material to match your switching device’s gate or trigger requirements.

Current Transformers for Sensing & Fault Detection

We build current transformers for instrumentation, panel-mount, and equipment-internal sensing applications  fault detection in critical electrical equipment, current sensing in security and protection panels, and similar low- to moderate-power sensing roles. Designed to hold calibration in service, not just at initial test. Utility-scale outdoor switchyard CTs are a different product class and outside our scope; we build the smaller-format CTs that go inside the equipment.

Antennas & Air Coils for RFID & Specialty Applications

RFID reader coils and proximity-sensor coils depend on precise resonant frequency and geometry. We custom-wind antennas and air coils to your exact frequency, Q, and geometry with conductor selection, shielding, and termination matched to your range and detection environment. We also build larger-format specialty antenna and air coils, including custom geometries up to roughly 2 ft x 2 ft for non-standard applications.

Why Engineers Choose Custom Coils

• 50+ years building precision components for demanding applications since 1967
• ISO 9001 certified, with full traceability and component-level documentation
• Built to your specified UL system where applicable, with documentation supporting your end-product recognition path
• RoHS-compliant documentation available for compliance submissions
• USA manufactured in Alcester, South Dakota domestic supply chain matters when a development program is running to a deadline
• Direct engineer access, every conversation is with someone who understands your application

Frequently Asked Questions

Q1: Can you manufacture RFID coils to a custom frequency specification?

Yes. RFID reader coils and air coils are wound to your exact resonant frequency, Q, and geometry. Whether your reader operates at 125 kHz, 134 kHz, 13.56 MHz, or some other frequency, we wind the coil to match with conductor selection and shielding matched to your range and detection environment.

Q2: What does a trigger pulse transformer do in a detection system?


It generates the fast, isolated pulse that fires the gate or grid of a switching device  thyratron, IGBT, SCR, MOSFET that in turn gates a higher-energy circuit. In detection applications, that’s typically firing laser pulse circuits or strobe lighting drivers. The key design parameters are pulse rise time, energy delivery into the gate impedance, isolation rating, and waveform repeatability across the cycle count your application sees in service.

Q3: Do you manufacture current transformers for fault detection?

Yes  for instrumentation, panel-mount, and equipment-internal sensing applications. Our CTs are designed to hold calibration in service, so the fault detection or sensing function stays accurate over the operating life of the equipment. We don’t build utility-scale outdoor switchyard CTs; that’s a different product class.

Q4: What are your lead times for custom security and detection magnetics?

4–8 weeks from finalized specification to delivery. Engaging us early in the design cycle is the easiest way to keep magnetics off the critical path during system integration.