DIY pin pointer

[Tibuck19]

Good evening Gentlemen I had made a pin pointer for my MMP using a AM radio soft metal core, It works great but I was wondering how long does that core need to be? about the length of the winding ?? or does it need to be much longer , Reason I ask is because it worked out so well I want to make another one for the Barracuda and a surfpi, but I only have one core left, I was thinking of cutting the 90mm it in half to make two out of one bar. what are your thoughts .


Photo of the pin pointer on the MMP

[Digger429]

Instead of cutting the bar in half, cut it only 40%/60% of the way along to get two bars of unequal length. Then make pinpointers from both. Then you'll have three different lengths to test, and you can then determine which is best and let us all know.

[homefire]

The length of the winding's and a bit seems to do the job for me.

[Tibuck19]

The length of the winding's and a bit seems to do the job for me.

Thanks , even though ferrite core are not expressive, I till I buy some, I only have the one and didn't want to chance cutting it, before I knew it was still going to work.

[jladre]

Definately you can cut it in haft.. thier will be no dufference in performance compare on the coil you posted.

[homefire]

The little flat ones from Cheapo AM radio's work fine too.

[Dave J.]

ferrite is a hard ceramic, takes forever to cut the stuff with a steel blade. A cutting tool "enhanced" with tungsten carbide or other super-hard grit will work better.

[homefire]

Just score it and it snaps a clean line.

[Tibuck19]

Definately you can cut it in haft.. thier will be no dufference in performance compare on the coil you posted.

Thanks ,

[Tibuck19]

Just score it and it snaps a clean line.

t
hat is exactly what I had in mind, make a score line and a clean snap like a plane of glass almost, I didn't think the flat cheepo am radio worked as well, I have a few of those. Thanks for the tip I ll definitely give them a try too.

[Tibuck19]

[QUOTE=Dave J.;233876]ferrite is a hard ceramic, takes forever to cut the stuff with a steel blade. A cutting tool "enhanced" with tungsten carbide or other super-hard grit will work better.[/QUOTE

I already snapped one in half by accident and I got a nice clean break , but thank you for the tip nonetheless

[homefire]

Only difference with the flat ones is the field is a bit more extended towards the Flat side and stronger on the narrow edges.

[bbsailor]

Good evening Gentlemen I had made a pin pointer for my MMP using a AM radio soft metal core, It works great but I was wondering how long does that core need to be? about the length of the winding ?? or does it need to be much longer , Reason I ask is because it worked out so well I want to make another one for the Barracuda and a surfpi, but I only have one core left, I was thinking of cutting the 90mm it in half to make two out of one bar. what are your thoughts .


Photo of the pin pointer on the MMP
[ATTACH]40201[/ATTACH]

See this web link for a good source of soft ferrites that work well for probe cores. http://www.surplussales.com/Inductor...s/FerRods.html I have used the (ICH) ROD 7.5/50 which is a soft ferrite .281" diameter by 1.969" long. Use a .25" rubber grommet on each end to hold the wire winding one and one half layers to two full layers of AWG 30 wire .024" diameter OD. Put a thin piece of copper wire under the rubber grommet to ground the ferrite. To minimize noise, you may want to put a shield over the probe winding to also minimize noise.

Soft ferrites do not hold their magnetic charge like hard or harder ferrites do. Just make sure that the probe works at your lowest delay setting. Ferrites material that has the least response or no response from being scanned like a target with a PI coil at low delays is a better ferrite to use to make a probe.

Joseph J. Rogowski