Hi Pot tester schematic

I have posted the equivalent schematic for my hipot tester.

The design is based loosely on some ideas from K8CU and AG6K.  However, I have simplified the circuit somewhat and used different components. The mechanical encapsulation is also different. I used LTspice to verify the tester before building it. The schematic is from the LTspice simulation (see below). I have also posted the simulation files so you can load them into your own LTspice simulator.

The unit consists of a 700VA 12KV AC RMS output (nominal) center tapped neon sign transformer that I purchased on Ebay. The trafo was designed for less than 230V AC RMS nominal primary voltage. Therefore the transformer gives out a bit more than 12KV AC RMS when supplied from the 230V AC RMS mains in Norway. After the rectifier I get approx 17-18 KV DC. The transformer is simulated by a sine voltage source in LTSpice. The transformer is insulated from ground in the tester for safety reasons. The schematic shows a gnd connection but that is only to get the Spice 3F4 solver to accept the netlist. It is recommended to insulate your tester from ground if you build one. There is a variac (not drawn on the schematic) in front of the transformer and the input is current limited by two 100W light bulbs in parallel (bulbs not drawn on the schematic). The voltage metering circuit is a uA meter with a shunt resistor and the current measurement instrument is a std. 100uA instrument protected by back to back diodes (not drawn on the schematic). The instruments are at high potential so adequate protection must be implemented to prevent arcs to the operator.  The device under test (DUT) is drawn. Note that a working tube has much higher resistance than 100 megs that is the load in the simulation. However this is placed as a load test for the simulation to check smoothing of the output voltage. The chassis is built in plastic and lexan and I have ensured long creepage distances by utilisation of vertical lexan insulators. There are no detected creepage currents at all even at full DC HV potential with my current design.

WARNING: do not attempt to build this high voltage device unless you are experienced in electronics and high voltage circuits. Touching the HV leads may instantly kill you. I do not accept any responsibility for your use of this device. The schematic is not a complete circuit description.

Download the LTspice simulation file here:  LTspice schematic of hipot tester

Video of the hipot tester in operation (test of an air variable capacitor):

High potential testing of an YC-179 high power vacuum tube

I have posted some pictures of the hi pot test setup of my new Eimac YC-179 vacuum tube (MRI pull). This is for a future legal limit (LA amateur regulations) amplifier for digimode and contest CCS amateur radio use. It is better to run a tube cool than to stress a smaller tube for high dutycycle modes. Let’s hope the tube behaves OK. It measured less than 15uA at 16KV DC from A to G so I might have a good pull. (The reason for measuring at such a high voltage is to ensure that the swing that the PI circuit contributes when driven by the tube can be tolerated w/o breakdown).

HV setup to test to 16 KV (below)

Tube in the test rig (below)

Click on the pictures to see the gallery (below)

The HV meter to the left is on the hot side of the rectifier / smoothing cap and has a multiplier shunt that gives 200 x. That means that 80 on the meter on the left indicates 16KV (DC) output. The uA meter on the right is in line and measures leakage current. (uA)  The o/p is current limited on this output. The meter panels are insulated with plexiglass and air gaps to prevent arc overs to the operator. Not that this would help since the HV leads are exposed. However in a future version… (below)   


Wireless infrared badger detector with 2,4GHz datalink to PC

We have 4 badgers in our garden that digs up our lawn. I needed a way to scare the badgers off without needing to use more drastic methods.

I have modified a passive infrared detector that I purchased at Clas Ohlson for another project several years ago. The modification makes the detector more sensitive. I take out the signals from before the logic that does an AND between sensor 1 and sensor 2. The signals are scaled down to 3,3V and are sent to two inputs of an Arduino mini PRO.

The modded PIR sensor with the uC and the radiolink mounted inside the existing chassis. (Note: the antenna is 1/4 wavelength, not 1/2 wavelength as is written in Norwegian on the picture)

The Arduino uC runs a C program that detects infrared thermal events. In case a valid detection is sensed, packets are generated and sent to a nRF2401 13 cm radiolink from Sparkfun. The radiolink sends the data to the base station in my house signalling that a badger is detected. I can then verify the operation of the sensor. Later the plan is to generate some noise to scare off the badger.


The sensor in its test configuration for detecting badgers. The sensor is mounted close to the ground to have their path in the sensors FOV.

Testing radiolink code with logic analyzer

Three wire signalling and nRF2401 chip control signals are analyzed.

Link check terminal. Good to check proper positioning of the RX antenna.


Good HF condx. A lot of DX worked lately.

The conditions lately have been very good on 20, 17, 15 and 12 meters. I have worked a lot of new stations on the HF bands above 40 lately. Finally the nice sound of a wide open high band that I remember from last time the SSN stayed above 100 is here again.

The SSN peaked above 100 between 12. and 13. April. The SFI also peaked around 14.-16. April. The K-index also stayed low and the auroral activity has been modest. Perfect settings for working DX!

Antenna: broadband vertical with computer controlled tuner. Large groundplane.
Rig: Yaesu FT-1000MP MKV
Power: 200W

PileUp! magazine with OH8X ARRL DX CW article PDF posted

I have posted the PileUp! magazine article that covers the OH8X (Radio Arcala) ARRL DX CW 2010 operation. The article also covers the antenna switching, the OH8X shack, the rotor systems and the full size 160m / 80m yagis. I have also covered contest experience itself and the contest results that ended in a new Finnish record. (Go to page 38 in the PDF for the article)

Download PDF

Download the PileUp! Magazine article as a PDF file

Goto page 38 for the arcticle