Surf PI - successful build

[Qiaozhi]

Basically, the circuit should be working ... as long as the trimmer is connected to the inverting terminal, and the reference voltage is connected to the non-inverting terminal of the comparator. The output is open-collector, so a pull-up resistor is required, or an LED with a series resistor. If you use a normal LED, then you can leave pin 1 connected to 0V. In that case the output will switch between +5V and 0V. However, the original Crossbow used a high-voltage diode, and in that case you need to connect pin 1 to -5V, so that the output voltage will swing between +5V and -5V. At the moment (on REV-B) pin 1 is connected to 0V, which is probably the preferred option for most people.

[Qiaozhi]

It still doesnt work George. I set the LED to come ar 10.5v then as I raise the voltage it stays on. I have to turn the preset
all the way round to get it to turn off. But it still does work properly if I remove the capacitor. But my circuit now is very noisy
and unstable since the last mod. I dont know if a coincidence or not or the time of night I am trying it, but before these mods the circuit seemed quite stable. I have checked and double checked to make sure I have followed your instructions.

I think I am going to leave the LED out. It seems to be giving me more trouble than its worth, and my board is starting to look messy
now.

This might seem a silly question, but I assume you have the capacitor inserted the correct way round? Or maybe the capacitor is faulty?

[chrisw]

It still doesnt work George. I set the LED to come ar 10.5v then as I raise the voltage it stays on. I have to turn the preset
all the way round to get it to turn off. But it still does work properly if I remove the capacitor. But my circuit now is very noisy
and unstable since the last mod. I dont know if a coincidence or not or the time of night I am trying it, but before these mods the circuit seemed quite stable. I have checked and double checked to make sure I have followed your instructions.

I think I am going to leave the LED out. It seems to be giving me more trouble than its worth, and my board is starting to look messy
now.

[Qiaozhi]

Hi George thanks for getting back to me.
So are you saying break the track coming from pin 1 and connect to pin 4. This means that Pins 1 & 4 will be connected to
the -5V.

Yes, that's correct.

Just one point. At the moment without the capacitor connected the circuit seems to work ok. Would this not be an easier fix?

The capacitor allows the battery voltage to rise slower than the -5V supply voltage, providing an indication at switch-on of the state of the battery charge.

[chrisw]

Just one point. At the moment without the capacitor connected the circuit seems to work ok. Would this not be an easier fix?

[chrisw]

Hi George thanks for getting back to me.
So are you saying break the track coming from pin 1 and connect to pin 4. This means that Pins 1 & 4 will be connected to
the -5V.

[Qiaozhi]

Hi Sven,
I was going to leave it out, the board works fine without the chip installed, but I have designed the decals for my box and I didnt want to have to change it. It works fine now without the capacitor. It will be interesting to see if your does the same as mine.

I went back and looked at the REV-A schematic, and there's a note above the battery warning circuit which says: "LM311 has pins 2 and 3 swapped over when compared with other comparators. The LM311 symbol legend is incorrect in this schematic. Adjust R50 to light LED when battery voltage is 10.5V."
I have corrected this in the REV-B layout.

However, under the circuit, there is another note: "Pin 1 should be connected to pin 4."
So, I suspect that's the root of the problem, as pin 1 is currently connected to 0V.

Please give that a try. If you can confirm the circuit works, I will update the REV-B Gerber files I previously sent to Sven. Hopefully, no boards have been ordered just yet.

[chrisw]

Hi Sven,
I was going to leave it out, the board works fine without the chip installed, but I have designed the decals for my box and I didnt want to have to change it. It works fine now without the capacitor. It will be interesting to see if your does the same as mine.

[SVEN1]

Chris I changed the tracks on my board as well yesterday. I have not put in the IC yet to test it out.Personally don't care if this feature is installed or not.............if it can be left out, fine with me.

[chrisw]

Hi George,
When I made the LED modification by altering the tracks it still didnt work.
The only way I can get it to work is to remove C26. I dont know if its the wrong size or just shouldnt be there or maybe its doing
its job and only letting the voltage drop very gradually. If this is the case I cant set it up correctly because the LED stays
on all the time once it triggers. I am not into electronics enough to understand this.
Will it hurt to leave it out or shall I change the value?

Chris

[SVEN1]

HI,
The Crossbow is not mentioned on my website at this time, just the Mirage.
The Crossbow was intended as a personal project after seeing the glowing reports of those that bought one of the orig. 12 Crossbows built by George.
Since it was not possible to purchase a built Crossbow, George sent me files etc. to build Rev. B, which was not tested built yet. I took on the project with two others and had 5 PCB's made.
Due to this or that, only one built was completed with good results with difficulty. Remember this is an advanced project like the Hammerhead, if you don't know what your doing............
Anyways, I sidelined the project for 2 years concentrating on the Mirage PI. On my Mirage builders forum for those that bought a PCB from me, a question was posted if I had thought about
ordering some more Crossbow PCB's and giving the project another try. There was enough interest to for a restart and order a min of PCB's. So 6 of us are attempting the build again.
A number of Geotech forum members are on board helping out with this project.
Chris has the first one working with superb results, the rest of us are somewhere along in the build.

Due to the latest posts on Geotech, some other members might be drawn to this project, which is great. For a first project, your better off with building George's Min-Pulse Plus before even
attempting the Crossbow. Right now consider the Crossbow project in Beta-mode.

George just send me Crossbow Rev C Gerber files which corrects Rev. B LED error on the PCB.
For anyone interested in a Rev C PCB, I will have a batch made to order once I reach a min amount of 10.
Due to currency value changes, pricing will be in US dollars.
$13.00 per PCB , plus shipping to the US $8.50, Europe $11.00
PCB's are of high quality.
Please PM me if interested.
I do have sub-forum set up with all Crossbow info for those who get a PCB from me to help those building the Crossbow.

[kenny444]

Sven has emailed me, said he will order C version boards, with correction (Thank you George) when he has an interest list of 10 persons. I have said I would take two units, the B series were $13 so something similar I would presume plus the postage etc Paypal accepted. If you want one contact Sven. Regards to all.

[chrisw]

Hi Guys,
Sven checks out these posts and Im sure will repond shortly. He is the man to speak to.

Chris

[sinclairuser]

i couldn't either, so i PM ed sven and they are not on yet, chris is a beta tester and sven said his is the first board running( of this board design).
he can explain better send him a pm, i would have grabbed a kit if there had been some, i have learned the lesson on this forum that you should grab kits when they come along.
even if you put them to one side for later on, i kick myself for not getting one of KT's cobras when he had them, always wanted a cobra and kt 315 did an excellent job oh well.
so even though i'm doing the mini pulse, and knocking up an arcade for a mate, i would have got one for a rainy day.

[kenny444]

I havent fixed my led problem yet but I made a video today showing the depth test on my Crossbow; its an awesome detector board check it out;

http://youtu.be/wH4avCfVdHk

Chris

Sorry can you direct me please? I went to the Treasurelinx site, but could not find the "Crossbow" only the "Mirage PI" is it the same thing, thank you very much.