lobo improved

[aft_72005]

No, i havent built and tested, as i said i 'm not happy whit it

Any way you’re working very well.

i would likel split design into 2 pcb

Also I am interest and waiting to see your split design.
What’s cad soft name that you designed lobo PCB?
Best regards.

[maxbiri]

I started split lobo schematic.
Here you find schematic and pcb for the first part:supply stage, tx stage, audio and battery check stage.
I do same other little improvement in supply stage for that i hope will be a better simmetrical power stage.

Bye Max

[maxbiri]

Here is a photo of milling pcb.

[guest]

lobo improoved

Maxbiri .
What software forPCB design you are useing ? How come pdf folder so small ?? Waiting to see your-final works lobo!!!bye

[maxbiri]

Hi all

All pdf are scale 1/1 300 dpi eccept schematic of course.

Bye Max

[maxbiri]

Attention!

I'm testing lobo's power supply stage and found a error, i will solve the problem and post a correct schematic and pcb asap.

Byr Max

[aft_72005]

Hi maxbiri
Please

What’s cad soft name that you designed lobo PCB?
Best regards.

[maxbiri]

Found 2 stupid error, one is a padstack of 78l05 with reversed pin and other is around 7660 external clock.
I will redraw schematic and pcb but this time i will post them after a good test.
Sorry for errors!

Bye Max

[maxbiri]

Hi all

I solved problem around 7660 and started whit same test and here happen strange things!
I tested same coil i have around.
With a 2.5 mH coil i have a strong distorsion in top side of sinusoidal so a check with a 0.7 mH coil.
Drivining final transistor at 5 V i can have a very good sinusoidal shape around 20 KHz with about 9.5 V pp and 2.4 mA but when i swich at battery power (9V) i have again good shape but only 12 V pp and 48mA!!!!!!!!!!!
Increase 68 R to 100 and 150 give a little less current but signal decrease around 11 v PP.
What about????????????

Bye Max

[porkluvr]

Hi all

What about????????????

Bye Max

Maxbiri,
(1) Any time you change transmit voltage supply you should adjust the drive level coming out of the 7555-pin7. Changing the emmitter resistance could also mean you should change the pin-7 pot's setting.

(2) As you change coils with different values of inductance you affect the transmitter tank circuit's natural resonant frequency; for optimum performance you should also change the parallel capacitor AND the setting of the frequency control pot near 7555-pin1 to obtain maximum output. After adjusting the frequency then you should re-check and adjust the drive level (1) for an undistorted coil voltage. These controls are interactive - you may need to do the adjustments several times. You should be aware that the frequency components and optimum drive level are not independent of each other.

I believe Tesoro makes two different coils for the LOBO but they both have very similar inductance and series resistance values. So, if you used either of the two factory coils then readjustment would not be necessary after initial setup.

Why don't you download LTspice and start getting familiar with it.
http://www.linear.com/designtools/software/

I will post a simulation circuit that you can use to visualize the information I just told you. I can't do it right now because I have something else pressing - I don't have the time - maybe tomorrow or later today. LTspice is pretty easy to use, but my circuit uses some models and symbols (potentiometer, MC33178, and LM393) that are NOT included with LTspice. These extras may need to be explained before they can be adapted into the simulation circuit.
There is LM555 included and some transistor models so you can perhaps set up the basic transmit circuit using fixed resistors -in the interim. Right click on components after they are placed and you will get the component attribute editor screen. You can enter an inductance value and add series resistance to the coil.

You would need to learn basic tasks such as placing components, wiring, rotating, mirroring and editing component value attributes. Google on "ltspice tutorial" to get some instruction, and also browse through the "Help" system.

If you simulate the circuit you can see that the potentiometer adjustments are actually quite critical; a small change in the drive level can cause substantial distortion of the phase reference voltage at the TX coil. You can also see the effects of changing frequency determining components.
Gotta go for now.

Oh I almost forgot to ask you: where are you measuring the current values that you mentioned?

[maxbiri]

Hi Porkluvr

Thanks for answer.
I forget said that every time i change coil i matched it with capacitor and setting 2 trimmer.
It's easy looking at oscope find the resonant F, it's the max amplitude point.
The strange is that when i set a coil feeding final transistor at 5 volt i have a good sinusoidal trace about 9.5 v peak- peak and a current about 2.4 mA misured in serie with R 68.
After i swich to 9 volt battery, only final transistor, and i have a bad sinusoidal trace; at this point i set the driver pot for having again a 9.5 pp undistorted signal and current misured on r 68 is now about 23-24 mA.
If i set driver pot for max tension pp i have about 48 mA and only 11-11.5 v pp.
I hope you can understand my poor english.
About PS, same years ago i used orcad ps but now i havent and i remember it was no easy to use it.
I need restart with PS, i know that it's a very powerfull soft but i need find time for restart from 0.

Bye Max

[maxbiri]

I try a simulation on input stage of lobo, the 2 ls204 form a passband centered on 13.45 khz and not 20!!!!!!!!!!! the gain at 20 khz is about 36.
Not very nice, i will shift a little the passband centering around 20 khz.

Bye Max

[porkluvr]

I try a simulation on input stage of lobo, the 2 ls204 form a passband centered on 13.45 khz and not 20!!!!!!!!!!! the gain at 20 khz is about 36.
Bye Max

I do not have simulation models and symbols for LS204. I use the MC33178 model because I think that
LS204 and MC33178 are reasonably close substitutes for each other.
Linear Technology does NOT manufacture a close substitute for MC33178, and this "third party" model require some extra effort to get working.

LTspice was originally crated to demonstrate LTC switching regulators so third party models are added extras that must be kludged in.
By using the XOPAMP.asy symbol and editing its attributes (see the attached screenshot),
many different opamp and the LM393 comparator can be simulated. ST products (TS922 for instance) use a different
virtual pinout, and the xopamp.asy symbol must be modified to conform to this oddity... the device pins are ordered in a different sequence.
I will not go into detail... they're a pain in the neck.

The phase response of the receiver section is just as or maybe even MORE important than circuit gain. The LOBO receiver amplifier components
determine a particular phase relationship to the TX phase reference.
RX gain is only part of the problem - receiver phase is also VERY important. Receiver section components impart gain but they also cause
the necessary phase change to rotate the received signal in relation
to the TX signal so that the ground cancelling (GCX) and discriminate (DISC) pots work correctly!!!

MC33178 and LS204 opamps exhibit a slightly higher dynamic range than most garden
variety low noise & low power opamps. (Output voltage swing is better). MC33178 is superior in this respect.
Otherwise, we could simply use an LT1007 model (included with LTspice),
for instance... or LT1784 might be useful... but, these are NOT suitable substitutes, only tools for simplification
should it be necessary.

Look at my posts in "Full m/lab SD2000 schematics" - there is more information, and also some CD4000 series models and symbols.
https://www.geotech1.com/thuntings/s...t=14001&page=6
Most (but not all) of the opamp models in the opamp.sub file can be used with the xopamp.asy symbol. Xopamp+.asy is different only
because the "+" input is on top.

I know I haven't told you everything, but it's been a long day. so I'm wrapping this up. Oh yeah, notice that I have grounded the
JFET gate resistors, otherwise there would be no pull-up in this incomplete circuit.

[porkluvr]

Whoops-something i forgot

I forgot to include the actual simulation file.

[maxbiri]

Hi Porkluvr

Very interesting stuf!
You are perfectly right phase is more important respect simple gain but as i said i'm not skill with pspice, i need more time for remember how set spice for phase schift.
I notice what i think is a error, not sure, but i think that 1.3 mH must be tx coil and 10 mH the rx coil.
I'm working using a about 1.3 mH tx, maybe this is the problem i have around distorsion in tx stage?

Byr Max