live wire toner/tracer - Page 1
Forum section: electronics / projects

author: antenna
author_rank: Frequent Contributor
timestamp: May 06, 2024, 01:50:05 pm
content: Looking for input on a little project. I want to be able to trace live 120v wires back to the breaker using my carlson super probe and was thinking about a twin t notch to block 60Hz, but I am unsure of what frequency would be best for the carrier signal. I worry that if I use something in the kHz, being connected to a long wire, I might cause interference to a sub or something else. If I go too high in frequency, it would couple between conductors and complicate tracing. Is there an industry standard frequency for this? I would like it high enough in frequency to be able to switch from an E field probe to a H field probe for when lines are shorted.Thanks!

author: antenna
author_rank: Frequent Contributor
timestamp: May 06, 2024, 05:44:20 pm
content: after building the 60Hz notch filter with components that could handle 120v, I realized how dumb that was. I wasted high power components when a high pass well above 60Hz would have done the same job. I also realized I need to put a high pass on the probe too because the line noise swamps the little signal I injected into the mains. Nothing like learning the hard way. I'm sure not making those mistakes twice.Edit: realizing there could be RFI on the mains too, I better use a BPF on the probe, not a high pass.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 06, 2024, 06:29:25 pm
content: The Klein Tools ET450 uses 33 kHz:https://data.kleintools.com/sites/all/product_assets/documents/instructions/klein/ET450%20Manual-web.pdfAll similar consumer tracers I considered were about the same.EDIT: For energized circuits, the tracers are quite inexpensive (<$25).

author: antenna
author_rank: Frequent Contributor
timestamp: May 09, 2024, 04:17:40 pm
content: I ended up using three 555's, one for 33kHz, another to modulate it at 2kHz, and another to change that ones frequency by about 700Hz using a mosfet to switch an additional timing capacitor on the 2kHz 555, so the tone alternates like the store bought ones.The carlson super probe worked good with a simple RC filter and a moderately shielded multi-turn current probe. The current probe, somehow, works on open circuits too, which I wasn't expecting with no current flow, but I know the loop isn't open because it picks up stuff the E field probe does not and does respond well to changes in probe orientation. I ended up using that silly 60Hz notch filter I made earlier, simply because it was already made and dropped the line voltage down to 1.3v as seen by the toner output, which has its own series of RC high pass filters too. Both the transmitter and receiver have gain control, so narrowing down the breaker when plugged into a live outlet works good when set just right. The only time I have issues is when I have a lot of RFI on a circuit, but in those cases, the current probe helps me find the source of that really fast too. Searching for RFI sources for my radio hobby just got a lot easier! I can hear what every wall wort and power supply is doing now, even which breaker has the offending noises ~ something a store bought live circuit tracer probably cannot do.They may be cheap to buy, and the one I quickly assembled for use at work tonight looks a bit unprofessional, but it was quite rewarding to build it and have it work as good as it does. What i thought was interesting is that LCD displays have more sounds using the H-field probe compared to the E-field probe. I can hear the data on my starlink antenna cable and all sorts of things now.