Barracuda Legend Kit Problems

[raygdunn]

Actually I meant .1 uF. Do you have any caps laying around? .1 -22 uF will do.

Hi Old cart,

Thanks for your input. I've just been retrying your test idea from some posts back.
Stabilising the 40106 power supply seems a great idea to stop interaction of the pulses, by adding a '104' capacitor across the power pins. I loosely hooked the wire ends over the pins, with a bit of spring tension rather than solder. That way I could monitor the effect, when I pulled the capacitor off. Surprisingly I could see none.


The crossfeed seems all over that chip. On pin 13 next to the Delay pot. I could even see a copy of the coil pulse. How that got there is puzzling.

The power supply lines looked clean, when monitored.

It seems common to the two boards, but maybe it will work differently for Impulse.

I'll see if changing the chips (40106, NE5534) has any effect, when they arrive. Probably not, but worth a try as I ordered some.

Ray

[Old cart]

This afternoon I spent some time testing different coils and I couldn't get rid of the spurious beeps either.

The coil I've been mainly testing has loose windings (0.95mm, 10" diameter, 338uH, ~1ohm, 96pF!), so maybe not a good choice. I think it made the most noise. The sound is like loose wire motion I must admit. The quietest coil was one with the coil embedded in silicone (16cm, 142uH, 1.6ohm, 294pF)

The first thing I noted was that it was most affected by vertical rotation, which shouldn't happen much in use.

The other significant thing was trying the coil on the PI-1. The noise was audible, but barely! It appears that the Barracuda goes full blast at the slightest detection, as would best suit a LED, buzzer or speaker.

Professional standard coil required for a very sensitive detector maybe?

(The other thing I noted is that the sound of the PI-1, is much less harsh ☺)

Ray

Noise is is vertically polarized so the coil must be held flat for lowest noise. If the windings can move relative to one another falsing will occur. However do not pot them in epoxy, it will increase coil capacitance. You can use tape to bind the windings or expanding foam. Many commercial detectors have coil shielding. Search this forum for the various techniques.

I think any testing that involves coil movement is not very useful until all other issues are resolved and the coil is stabilized and possibly even shielded. Shielding may not be necessary at long sample delays, if the coil is small, or is to be used underwater.

i think the problems with spurious noise on the sampling lines might be affecting the overall detector noise and is due to power supply noise. Check each of the supply pins (+/- where applicable) on each chip relative to the negative side of the battery. Particularly when doing noise tests it is very important to locate the ground lead carefully ( the - side of the input protection diode is a good place) and to turn off all external sources of interference. Disconnect any PC peripherals and run the PC off batteries where practical. While checking the supply pins also check all the ground pins on each chip. Use AC coupling on the scope if it is available and the use the max sensitivity possible. Set the bandwidth limit to the lowest setting possible if available. Show me any pictures of any line that has more than 50mV of noise on them and identify them by chip name and PIN number. This is probably pushing the limits of what most USB scopes are capable of.

[raygdunn]

Barracuda... Beeping Beeps

This afternoon I spent some time testing different coils and I couldn't get rid of the spurious beeps either.

The coil I've been mainly testing has loose windings (0.95mm, 10" diameter, 338uH, ~1ohm, 96pF!), so maybe not a good choice. I think it made the most noise. The sound is like loose wire motion I must admit. The quietest coil was one with the coil embedded in silicone (16cm, 142uH, 1.6ohm, 294pF)

The first thing I noted was that it was most affected by vertical rotation, which shouldn't happen much in use.

The other significant thing was trying the coil on the PI-1. The noise was audible, but barely! It appears that the Barracuda goes full blast at the slightest detection, as would best suit a LED, buzzer or speaker.

Professional standard coil required for a very sensitive detector maybe?

(The other thing I noted is that the sound of the PI-1, is much less harsh ☺)

Ray

[Old cart]

Very good with the carbon fiber. Is there any metal attachment hardware within a foot or two of the coil? What kind of PC are you using? A laptop or desktop? Does it have any other hardware attached to it other than a mouse or keyboard? If it is laptop can you run it on batteries?
The reason I am asking all these questions is trying to figure out how noise is getting into you system. The cap should have stopped the detector from working unless it is bad or on the wrong pins of the 40106. You want the minus on pin 7. Does your meter read capacitance?

[Impulse]

we can attack later if you wish.

Yes up for that once we get this board to function properly

[Impulse]

It's a carbon fiber hiking stick. And the cap stopped the board from working so I have taken one side off for now.

[Old cart]

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Well you are coming right along. I see one problem. It appears that the you have metal shaft going down to the coil. That is a no-no. If the coil moves at all relative to that rod the detector will sound off. Worse it forces you to sample later than you normally woud have to or set the threshold lower. Both will reduce the sensitivity of the detector significantly.
NO METAL IS ALLOWED with 18" of the coil.
Anxious to see what the sampling pulses look like after your installed the cap. I actually see several bad design practices on the board that we can attack later if you wish.

[Impulse]

[Old cart]

Ok once I get my pc back up and running I will upload the scope shots

Here's my test set up I have tried it in the garden and still beep beep beep in mid air. I live next to the coast the most powerful electrical thing near me is my TV and I turn it off when I am testing the board.

I did not see any photos. The still could be some kind of noise generator near your house. All your traces have a fair amount of noise. It could even be your PC which are notoriously noisy. If you compare you sample gates screen shots to Ray's you will note several times the noise. I don't know if this is coming from your scope PC or something else. Can you stil borrow the fluke scope from you work place? Maybe we should give that a go.
i worked for Tektronix for 31 years so I am very aware how much differences they are between expensive and hobbiest grade equipment. This is not to criticize anyone, but just to say that we need to be aware of test equipment limitations.

BTW I did a little research and saw some comments saying that that people had damaged their PC using USB based oscilloscopes. I have no idea what they were measuring but certainly it is possible since they are electrically connected. More expensive PC connected scopes use what is called galvanic isolation which just means they are not electrically connected to the PC. I think many use optical isolation.

[Impulse]

Does beeping still exist even you sweep the coil at 1 meter above parallel to the ground?

Yes it is there no matter how high off the ground it is

[Impulse]

Ok once I get my pc back up and running I will upload the scope shots

Here's my test set up I have tried it in the garden and still beep beep beep in mid air. I live next to the coast the most powerful electrical thing near me is my TV and I turn it off when I am testing the board.

[Old cart]

I have swapped the cable for a peice of coax and now my pc won't work again. I still cannot move it without it giving a false signal

This must be very frustrating... All these motion problems! Show me a clear picture of the coil, cable, board end of cable and general surrounding pics. Do you have any radio stations. industrial plants or large electrical equipment like power lines near your house?
if no take on of you coils and connect it to the scope, no detector just the coil and the set the scope to the most sensitive range.
try 5 uS per div.

[jladre]

I have zip tied the cable down and the connections are solid I have the coax core as the + and the shield as the -. The coil is glued to a piece of thick cardboard and then glued to the shaft that I am going to use

Does beeping still exist even you sweep the coil at 1 meter above parallel to the ground?

[Impulse]

"Beep...beep..beeep" sound?
Be sure that your coil cable has a good and not loose connection, the screen must properly connected to the ground, and last be sure your coil is properly fix to the shell so that it will not have movement inside during sweeping.

I have zip tied the cable down and the connections are solid I have the coax core as the + and the shield as the -. The coil is glued to a piece of thick cardboard and then glued to the shaft that I am going to use

[Impulse]

This is progress! Try depth test now. Have you got a .1uf cap? If so please solder it, with the leads cut as short as possible. One the back of the board between pins 7 and 14 on the 40106. Remember the pins are upside down and reversed becuase this is the back of the board so confirm before soldering.

on second thought this dual core coax probably has high capacitance. Swap it for coax as soon as you can.

I have swapped the cable for a peice of coax and now my pc won't work again. I still cannot move it without it giving a false signal