How to work out tubing, transformers and electrodes
Getting the transformer right makes a neon sign bright, reliable and long lasting. Here is how to work out the glass, transformer and electrodes for a job.
1. Measure the glass
Measure the length of each section along the tube, in metres, and add them up. Count the sections too, because each one adds two electrodes to the circuit.
2. Choose the gas and tube diameter
Smaller tubes are brighter but need more voltage per metre, so a transformer runs less of them. Neon needs a different voltage from argon, so decide the colours first. Our neon glass colour chart shows the stock colours and sizes.
3. Work out the voltage
Each metre of tube and each pair of electrodes needs a certain voltage. Our neon calculator adds this up for 8 to 20mm tube, for blue and neon gas, and suggests Hansen and SIET transformers.
4. Choose the current (mA)
Match the current to the tube size and the electrodes: lower currents such as 18 to 25mA for small tube, higher currents for large tube. The electrode picker checks the electrode is rated for the current you choose.
5. Pick the transformer
Choose a transformer whose output voltage covers the total, without loading it to its limit, and split big signs across more than one transformer. As a rough guide, an 8kV transformer runs about 10.2m of 10mm glass or 14.1m of 15mm glass, depending on the number of sections.
6. Check the installation
Keep HT cable runs short, use cable and caps rated for the voltage, and install to BS 7671 and EN 50107. Neon facts covers touching height and fire-fighter's switches.
Learn more
- How to make a neon sign, our first tutorial, with a training video.
- Neon Techniques, from the Museum of Neon Art shop, and The Neon Engineer's Notebook from Lightwriters Neon Chicago.
Not sure which transformer you need? Call 01892 783 900 with your glass lengths and we'll help.