433mhz fs1000a circuit diagram

Thread Starter

denison

Joined Oct 13, 2018
302
Hi All, I know you don't need to know the internal parts of for example the fs1000a transmitter to use it. However this is not very satisfying. I want to know how it is built.
Does it have a multiplier circuit for instance? I have seen these used on much lower frequencies. But 433mhz seems too large for a multiplier. I have used a AD633 multiplier in a LTSPICE simulation with a 10k carrier frequency.
Can anybody give me the circuit used in the FS1000A transmitter? I guess somewhere there is a crystal oscillator.
 

Ya’akov

Joined Jan 27, 2019
6,266
Here is a schematic for the FS1000A (unfortunately the text is blurry Russian but the schematic is readable):

1659607234854.jpeg
It is a SAW filter based oacillator. Surface Acoustic Wave filters are convenient little things that can be used at very high frequencies. In conjunction with C1 and C2 you have a pi filter that acts with Q1 to do the necessary phase shifting to get oscillation.

The little can that looks like a coin cell on the FS1000A is the SAW.
 

Thread Starter

denison

Joined Oct 13, 2018
302
Here is a schematic for the FS1000A (unfortunately the text is blurry Russian but the schematic is readable):

It is a SAW filter based oacillator. Surface Acoustic Wave filters are convenient little things that can be used at very high frequencies. In conjunction with C1 and C2 you have a pi filter that acts with Q1 to do the necessary phase shifting to get oscillation.

The little can that looks like a coin cell on the FS1000A is the SAW.
Thanks YA'AKOV. The transmitter circuit is not that complicated. But the receiver circuit now that is complicated.
To get a good 433mhz transceiver with good security I am going to use a HT12E encoder with the transmitter and a HT12D decoder with the receiver. A dip package for the decoder was available at Element 14 but couldn't find a dip for the encoder. Found both on e-bay but from China. Not an ideal source but had no choice and ordered from China.
 

Ya’akov

Joined Jan 27, 2019
6,266
Thanks YA'AKOV. The transmitter circuit is not that complicated. But the receiver circuit now that is complicated.
To get a good 433mhz transceiver with good security I am going to use a HT12E encoder with the transmitter and a HT12D decoder with the receiver. A dip package for the decoder was available at Element 14 but couldn't find a dip for the encoder. Found both on e-bay but from China. Not an ideal source but had no choice and ordered from China.
Just a heads up. If oyu are in the US, there are severe restrictions on the use of the 433MHz band you need to be aware of. Unlicensed operation in any band above 70MHz not otherwise regulated has the same restrictions.

The band is restricted to remote control and status signals (e.g.: alarms) You can't use the band for data transmission except as part of a control signal. If the transmitter is manually operated it must transmit for no more than five seconds after the operator stops keying. If the transmitter is automatically operated it may be on the air no more than five seconds at a time.

However, very low power intentional radiators in the band can by pass these restrictions but are then controlled by this paragraph:

In addition, devices operated under the provisions of this paragraph shall be provided with a means for automatically limiting operation so that the duration of each transmission shall not be greater than one second and the silent period between transmissions shall be at least 30 times the duration of the transmission but in no case less than 10 seconds.
So, 433MHz is a pretty bad band for data transmission in the US and in other regions it is also regulated as a different service. If you want to do data transmission I would strongly suggest 2.4GHz using something like the [nRF24L01+] [based boards] that are readily available and don't have this problem.

1659689729557.png

(there are cheaper and more expensive boards, the cheaper the dodger is the general rule RF cans on the board are a good sign, you will want these too, I promise).

1659689792275.png

They also offer sophisticated channelization of the data streams and other very useful features like guaranteed delivery. There are Arduino libraries, and lots of tutorials.


NOTE: Andreas uses convention in his code controlPak and displayPak that are not part of the nRF24 library, just his choice for naming his data structures.

Operations in contravention of the FCC rules may seem harmless but the chaos a rogue transmitter in one of the unlicensed remote control bands can wreak is surprisingly prodigious. It is far better to stay inside the rues and do the right thing, even if it seems to be mostly harmless.

If you have any questions about this direction, please do not hesitate to ask!
 
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