300MHz RF module - Page 7 - Electronic Circuits Projects Diagrams Free

audioguru · 9th January 2007, 03:18 AM

Quote:

Originally Posted by bananasiong

So the fastest switching time is 2.85 ms per bit right?

Yes but only when the PLL is tuned exactly to the modulating frequency. If it is not exactly the same then it needs additional time to lock to the modulating frequency.

The super-regen receiver has some capacitors that attenuate its squegging oscillation that might also slow things down.
I think the receiver is designed to slowly switch a relay on and off.
CHEAP, CHEAP, CHEAP, CHEAP stuff works poorly.

mramos1 · 9th January 2007, 10:12 PM

Quote:

Originally Posted by audioguru

I think the transistor is the 300MHz oscillator and it is turned on and off at an audio frequency by the classic Cmos oscillator made from two Nand gates.

The Cmos oscillator can be stopped by diconnecting the input of one gate from the circuit and grounding it, then started with a resistor that pulls the input high.

How small could something like this be made and how low could the power be reduced to? Like 1.5 or 3 volts, maybe pulse it?

Hero999 you input is welcome as well. I have a need for this as well. Not trying to hijack the thread.

audioguru · 9th January 2007, 10:56 PM

The transmitting transistor would transmit very low RF power with a low supply voltage. So its range will be small.
An ordinary Cmos gate has a minimum supply of 3V but its output current is very low. A 3V battery's voltage drops to 2V over its life. A 74HCxx Cmos gate has a minimum supply voltage of 2V and has a higher output current.

What good is a transmitter that is not turned on? Hardly ever used like a car door remote entry?

bananasiong · 9th January 2007, 11:41 PM

Quote:

Originally Posted by Sceadwian

Mind you there is always a flux residue afterwards that needs to be dealt with, sometimes acidic and VERY bad if left in place.

What is a flux residue? Need to clean it up after using the liquid flux?

How do I calculate the frequency of the Cmos oscillator?
Why I can't do it like mentioned previously, just add a pull up resistor. From your schematic, the transistor also acts as a switch right?

Thanks

Sceadwian · 9th January 2007, 11:48 PM

The flux basically 'floats' to the top of the soldering joint once the solder hits it and leave a residue over the top of the joint, some types of flux leave a corrosive residue which needs to be cleaned off afterwards. Depends on the flux.

audioguru · 10th January 2007, 12:22 AM

The Cmos oscillator turns on the transmitter and turns it off. Then the modulation is digital AM.
The calculation for a classic Cmos oscillator is here:

bananasiong · 10th January 2007, 08:08 AM

Where are the values from? 0.559 and 0.455.

audioguru · 10th January 2007, 01:40 PM

Quote:

Originally Posted by bananasiong

Where are the values from? 0.559 and 0.455.

MM is an IC prefix used by National Semiconductor so it might have been on their applications note. The same formula is in my "Cmos Cookbook" written by Don Lancaster.

bananasiong · 10th January 2007, 02:24 PM

From the attachment, it says that if the supply is higher, the higher it can oscillate, means frequency?

The receiver is really pO.or
After it is tuned well, the next day or after it has been turned off for a while, I need to re-tune it, or else I cannot get the signal transmitted. And sometimes, no matter how I tune it, it just wouldn't work. Then it worked the next day -_-"
Now it is not working, maybe I'll try it tomorrow..

Thanks

audioguru · 10th January 2007, 02:38 PM

A Cmos inverter or gate has a higher output current with a higher supply voltage so it can switch faster. I use a two-inverters Cmos oscillator at 1.6MHz on a 12V supply and it works well.

I think your receiver is crappy. Cheap, cheap cheap!

bananasiong · 10th January 2007, 02:51 PM

Yea, really crappy, cheap, and poor! It isn't worth as its price. The parts can be got easily, only the pcb I cannot make it.

9th January 2007, 10:56 PM	(permalink)
audioguru Experienced Member	The transmitting transistor would transmit very low RF power with a low supply voltage. So its range will be small. An ordinary Cmos gate has a minimum supply of 3V but its output current is very low. A 3V battery's voltage drops to 2V over its life. A 74HCxx Cmos gate has a minimum supply voltage of 2V and has a higher output current. What good is a transmitter that is not turned on? Hardly ever used like a car door remote entry? __________________ Uncle $crooge

9th January 2007, 11:48 PM	(permalink)
Sceadwian Experienced Member Blog Entries: 1	The flux basically 'floats' to the top of the soldering joint once the solder hits it and leave a residue over the top of the joint, some types of flux leave a corrosive residue which needs to be cleaned off afterwards. Depends on the flux. __________________ Curiosity killed the cat; That's why they have nine lives.

10th January 2007, 08:08 AM	(permalink)
bananasiong Experienced Member	Where are the values from? 0.559 and 0.455. __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

10th January 2007, 02:24 PM	(permalink)
bananasiong Experienced Member	From the attachment, it says that if the supply is higher, the higher it can oscillate, means frequency? The receiver is really pO.or After it is tuned well, the next day or after it has been turned off for a while, I need to re-tune it, or else I cannot get the signal transmitted. And sometimes, no matter how I tune it, it just wouldn't work. Then it worked the next day -_-" Now it is not working, maybe I'll try it tomorrow.. Thanks __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

10th January 2007, 02:38 PM	(permalink)
audioguru Experienced Member	A Cmos inverter or gate has a higher output current with a higher supply voltage so it can switch faster. I use a two-inverters Cmos oscillator at 1.6MHz on a 12V supply and it works well. I think your receiver is crappy. Cheap, cheap cheap! __________________ Uncle $crooge

10th January 2007, 02:51 PM	(permalink)
bananasiong Experienced Member	Yea, really crappy, cheap, and poor! It isn't worth as its price. The parts can be got easily, only the pcb I cannot make it. __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Latest
Chip talk	dreamproject	Electronic Projects Design/Ideas/Reviews	8	2nd April 2005 07:24 PM
Motor control interface	dreamproject	Micro Controllers	0	31st March 2005 03:48 AM
controlling laser module via RF receiver	mr. mister	Robotics Chat	1	28th February 2005 03:45 PM
ignition module	induction1	General Electronics Chat	5	24th November 2003 11:34 PM
Safety interlock module	wilfredmike	Electronic Projects Design/Ideas/Reviews	6	2nd November 2003 08:41 PM