Progress

[MightyGuru]

Well I have finally got all the parts and PCB's. I got the Li-Poly battery board assembled and tested last night. I have been taking picts and will start a new post of my progress soon. Thank you for all your images and insight!

[rys]

I really need more sleep, heh.

For those of you that didn't see it in the Parts List thread, I am currently on the PLL stage. I also mentioned that I am traveling -- someone asked for how long -- I will be gone only a few weeks and should be back by mid July.

I am missing C77 (filter cap) for the PLL stage, so I am unable to fully test. C77 is a filter cap, so the PLL should work without this part placed (in my opinion), but I plan on placing the part as soon as I get back and can place a parts order.

Right now the PLL "sort of" works. Needs some debugging.

Notes from last night (PLL Stage):

If you thought the VCOs were a pain to solder, get ready for the 0603 parts. It takes a little practice, but soldering 0603 isn't that bad. There are just quite a few of them, so it will take a while.

Microscope and/or good optics are essential for this stage. You will need good tweezers, solder wick, and a good iron.

It's entirely possible to use hot air and solder paste, but extreme care must be taken for several reasons. The first being that you can blow away an 0603 component pretty easily, even with hot air set on low. Second, being that the board will only stand up to so much thermal shock before delaminating. Lastly, the entire ground plane for the RF stage acts as a heat sink. It's possible to reflow components on the opposite side of the board - Although they should stick due to surface tension of the solder.

It isn't required, but having a brush and flux near (for reconditioning your soldering tip), or having spare tips for your iron is very helpful.

The Crystal: For the first time, I actually used hot air to mount a component on this project. I really dislike using it, but saw no other way to mount the crystal. The pads are basically right beneath the part, with very little visible pad on the sides (once the component is down). I didn't want to destroy the crystal with the heat of the iron. There are some great videos on SparkFun showing the proper technique for mounting a part with hot air. Tin the pads by hand (or use paste), then heat and place.

Tests

This is going to sound silly, but with the lack of sleep, etc. I can't recall if I got 2.49v from the PLL power regulator, or 2.20v. Obviously the latter would be a problem. I will check it as soon as I have a chance.

The crystal is being driven by the PLL properly, I'm getting approximately 20-22mhz on it.

PLL1 test code shows noise on the pin 10 of the PLL.

PLL2 test code programs into the AVR fine, but output is not as expected. I am not getting 0.00-2.20v at the 10k resistors.

I was unable to verify the VCO test, since I do not have a spectrum analyzer. Vcc on the VCO has +12v. All voltage rails from the power supply stage are correct (3.3, 4.95, 12, 27).

Next steps

I will need to verify voltage to the PLL as soon as I have a chance. Although the PWM and 555 sawtooth stage tests were functioning correctly. I am going to go over the LM358 area again and verify the output into vTune on the VCOs.

More soon...

[Superworms]

ha ha ha. that was me who asked how long you were going to be gone

[MightyGuru]

Dont forget to install C20!

Joke right? C20 is do not place.

Personal observation. Looking at the datasheet for the LM2733X it is strongly recommended that C20 be used. According to the datasheet:

Although internally compensated, the feed-forward capacitor Cf is required for stability. Adding this capacitor puts a zero in the loop response of the converter. Without it, the regulator loop can oscillate. The recommended frequency for the zero fz should be approximately 8 kHz. Cf can be calculated using the formula: Cf = 1 / (2 X π X R3 X fz)

Based on your circuit values and the above formula: C20 = 199pF

[MightyGuru]

Another observation is the value specified in the schematics for C20 (160pF) is incorrect based on the before mentioned formula. If calculated the value should be around 538pF. Maybe this difference was the reason/cause of the 'odd' behavior which prompted the designer to leave it out??

[rys]

Small update. I am leaving on my trip tomorrow, and have had little time for working on the WB.

I tested the PLL stage and currently the voltage regulator is completely down. (At one point it was functional, and the PLL was driving the crystal, but now the enitre stage is down.) Maybe a pin shorted to ground or something silly.

Once I return I will strip the parts past the voltage regulator and see if there is a bad connection somewhere.

In the interim, I am excited to post that I created a heavily modified and stripped down version of the wavebubble firmware designed to test the VCOs. It successfully jams using both VCOs in close proximity of my cell phone. (Within a few inches -- Gain stage is not installed yet - waiting for a functional PLL).

MightyGuru, thanks for the update on C20, I will see about placing it when I return. Excited to see your progress, keep up the good work.

[MightyGuru]

Light at the end of the tunnel
Would you mind sharing your 'modded' firmware?

[rys]

Sure thing,

Here is the Modified Firmware.

It's basically missing the PLL entirely. I will caution however that use of this firmware is at your own risk. If vTune exceeds the absolute max of your VCOs, or attempts to tune too low, you can accidentally blow one or both of the VCOs out.

The tuning numbers for dcoffset and bandwidth are actually taken from the config page of the Wavebubble project. While these numbers aren't exact, they're good enough for testing.

Again, use at your own risk. I'd recommend a few checks prior to using the code:

1. Verify the PWM test.
2. Verify the sawtooth High / Low test.
3. Verify the digital resistors test.
4. Ensure that you have attached D5 and D6 (protection to the VCOs) for going below ground.
5. Verify the switches tests.
6. Verify the output from the LM358s, that they are within range of your VCOs. (For this code).

(As a rule, this all should be performed before the VCOs are actually attached to the board).

Once everything checks out. You can attach the VCOs and wave guide wire antennas, and run the code.

Good luck!

Edit: I should also point out that, if you are in posession of a spectrum analyzer, it's possible to build the WB without the PLL entirely, tuning would need to be performed by hand. A modified firmware like the one located above could be used, it could even be further modified for multiple programs.

[rys]

I'm still alive! Just waiting on replacement PLL parts to arrive.

In the mean time...

Wavebubble works with iPhone

[WBVenom]

Excellent pictures and documentation. Your battery solution is most elegant. Is that typically the finished solder quality you get with non-leaded solder? Doesn't look like you're able to get smooth fillets on most of your components.

Excellent work though! Very helpful!