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[SOLVED] TX-2B RX-2B circuits. question about several components

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Shachar85

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Hi
I would like to build a small project with remote control.
I found that TX-2B RX-2B are the main components that I need, and found this pdf:

which tells me how to build the circuit I need (page9).

1.will it make difference if I used 150p capacitor instead of 151p and 500p instead 501?
2. what is L3 inductor in the right side of the upper circuit? (0.3mmX5mm?)
3. what are the two M in the lower circuit?
4. there's a resistor on the lower circuit, just above the RX-2B that says 3.9MO. does it mean 3.9 mega ohm?

thanks for any help

---------- Post added at 02:14 ---------- Previous post was at 02:14 ----------

the pdf:
**broken link removed**
 

Hi,
sounds you are not very experienced with electronics? Well, here are some answers:
1) third number is exponent. 151p means 15 x 10^1 ==> 150pF (153pF would mean 15 x 10^3 ==> 15000pF)
2) L3 is the inductor for the LC resonance circuit. Important for the RF frequency and radiated power. I assume they describe 7turns of 0.3mm copper wire with 5mm radius.
3) As the application describes an RC car, these are the motors for driving and steering
4) yes, 3.9MegOhm
 
yes, I'm not very experienced with electronics.
I haven't done anything with electronics in years and I try to start again.

about the L3 - I buy all the components in ebay and I couldn't find inductor with those dimensions.
can I use something else that would give me the same result? or maybe you know where i can buy such inductor on-line?
 

L3 is labeled as 6.8 µH. Just shop for that value.
 

L4 is labeled 6.8 uH
L3's label is below it
 

Okay, sorry. Since they didn't give any turn spacing information I can only estimate the inductance at 0.25 µH. Here's how to make the coil: An introduction to the air cored coil.
 
Last edited:

Shachar85 said:
about the L3 - I buy all the components in ebay and I couldn't find inductor with those dimensions.
can I use something else that would give me the same result? or maybe you know where i can buy such inductor on-line?
Click to expand...
IMHO calculating the inductance and searching for an adequate part is more effort than making one by yourself.
Oscillator coils are usually single wound air cored coils. L3 was describeb 7turns of 0.3mm copper wire with 5mm radius.
So buy (isolated) copper wire of 0.3mm. Look for something round with 5mm diameter (pencil/screwdriver/nail) and wind 7 turns of copper around. Thats it!
The link KJ6EAD posted is also a good description how to make, and contains a picture of how such a coil looks like.
 

actually it sounds like more fun to the project

thanks a lot for all your help!
I'll start ordering components today
 

guys, few last questions...
I couldn't find 1.1uH inductor. could I add 1uH and 0.1uH in series and get the same result?
couldn't find a 3V zener diode. will 3.3V do?
about making a coil. I searched eBay for copper wire. this is what I found:
**broken link removed**
its supposed to be for jewelry, but copper is copper, right? will that do?
 

As L1 is only used in the stimulation path for the main LC Oscillator (L2), I would try to use 1uH instead of 1.1uH. IMHO this part is not critical.
3V3 Zener will work also, as VDD of ICs is specced 1.5V to 5V.
Copper wire: looks good. Please ensure this is isolated copper (enamel coated).
 

thank you very much for your answers!
 

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