Introduction: Assembling a Niftymitter V0.24 Board - a Short Range FM Transmitter

This Instructable will guide you through assembling the circuit for Niftymitter, an open source mini FM transmitter. The circuit uses a free running oscillator and is based on Tetsuo Kogawa's Simplest FM transmitter.

The project is housed at www.openthing.org/products/niftymitter

Step 1: What You Need


Step 2: Solder on the Resistors and Capacitors

Place comonents flush up against the board from above. After soldering the legs onto the pads, trim of the excess.
Start by soldering all the resistors. Follow with all the capacitors and the jumper lead. Ensure that the electrolytic capacitor is oriented as described on the circuit layout diagram, the negative side away from the socket.

Step 3: Solder on the Socket, Coil and Trimcap

Next solder on the socket. Take care to ensure the socket is solidly soldered on. Solder on the trimcap, taking care to orient the flat side as shown. Then add the coil. The instructable for making the coils is here.

Step 4: Solder on the Transistor

Finally add the transistor, taking care to orient the pins correctly.

Step 5: Add the Power Connections

Solder on the positive lead from the PP3 clip to +9V. Add a short length of wire to the ground connection.

Step 6: Prepare the Switch

Bend the positive lead of the switch LED around one of the switch pole legs as shown. Solder and trim the LED leg as shown. Bend over the remaining LED leg to make a loop.

Comments

author
SulabD (author)2015-10-27

Can i use 2N3904 transistor??

author
royshearer (author)SulabD2015-10-27

I don't know I'm afraid. The design comes from Tetsuo Kogawa, so might be worth asking him:
http://anarchy.translocal.jp/

author
Txer (author)2015-05-02

I don't mean to be funny here .but how does a 10pf manage to get you on the fm band I only find that 30pf and above gets me on fm band .or is because in different country's the fm band is different ?

author
royshearer (author)Txer2015-05-04

I'm afraid I have no idea why it works but the 10pf has been fine evry time for me in the UK..

author
lseemann (author)2013-06-05

nice work. i want to build one. can i replace the 9V battery with USB connector? Would it be enough its 5V 1A to power the device?

author
sciencetor2 (author)2012-07-07

are solder lines on an all purpose radioshack pcb not an option here as an alternative to etching?

author
royshearer (author)sciencetor22012-07-18

I'm not familiar with that - tell me more!

author
sciencetor2 (author)royshearer2012-07-19

well basically its a prototyping board, its a prepunched pcb grid with each hole having a copper circle around it, and you draw paths with solder rather than making a print of the paths ahead of time, would using solder as thhe conductor be an issue?

author
jtc10512 (author)2012-03-08

is that pink thing in the center the tuner?

author
royshearer (author)jtc105122012-03-09

Yes, it is the trimmer capacitor, tuned with a trim tool or screwdriver.

author
alexanderall (author)2011-05-17

Where does the switch go on the on the pcb?

author
burdockwing (author)2011-04-13

so wait what does this exactly do?

author
royshearer (author)burdockwing2011-04-15

Niftymitter broadcasts any audio signal that you put into it on FM radio over about a 20m radius so that you can listen in using a FM radio. like an iTrip.

author
technozook (author)2011-03-16

could you post a scamatic cus i cant etch my own board

author
royshearer (author)technozook2011-03-16

Schematics can be found at Tetsuo's site here:
http://www.translocal.jp/radio/micro/howtosimplestTX.html

Or as a .png here:
http://niftymitter.googlecode.com/files/niftymitter%200.23%20electronics%20schematic.png

Or as a eaglecad .sch (not a very good one at the moment to be honest - please improve) here:
http://niftymitter.googlecode.com/files/0.23.sch

author
bobrob5k (author)2011-02-26

is it possible to make this work with out a battery?

author
royshearer (author)bobrob5k2011-02-28

I would imagine so, just use a 9v power supply in place of the battery?

author
coolacid (author)2010-01-19

What goes in the Y-ish symbol between the 9V and the GND?

author
cliffyd (author)coolacid2010-12-15

its for an antenna wire.

author
royshearer (author)coolacid2010-01-24

 That is a hole to solder on an antenna if you fancy. I don't know much about how one should do that. Will annotate it better in future versions.

author
______ (author)royshearer2010-11-26

check out my new reciving and/or transmitting antenna Ins. soon today

author
______ (author)______2010-11-26

The slide show is out

author
______ (author)royshearer2010-11-26

Yup

author
coolacid (author)royshearer2010-02-15

Nice! I made mine and tested it. I really works. It's kind of tricky to tune it, but it's awesome anyhow.
But there's an annoying buzz in the audio. I was wondering if it's something I did or if it's a known issue.

author
royshearer (author)coolacid2010-02-16

That's great! The tuning is tricky indeed, and definitely needs improving. Buzzing is not a known issue in the units I have made. That kind of thing normally suggests a problem with grounding somewhere in the circuit - check all connections to the negative terminal of the battery are good?
Otherwise I imagine it might be a tuning issue still, or the signal might be distorting if the input level is too loud, in which case you could try turning the volume right down on whatever your source is..

author
expert_vision (author)royshearer2010-11-02

I also experience a buzz in the audio and it persist even if I unplug audio input. As a power source I use a PC PSU's 12V line with a 2.7V zener, so i get 9.3V. May be I should try a 9 V battery or 3V zener or a stabilizer.

author

The buzz was because of the PC fans .. LOL. Also any PC activity cause small disturbance on the PSU DC voltage lines. So the VCC has to be pretty stable(like a battery).

author
royshearer (author)expert_vision2010-11-06

Oh right, that makes sense.

author
______ (author)2010-11-26

Has anybody but me built it and tested range. Range is 1 foot to 250 feet!

author
guitarmaster101 (author)2010-10-13

Is there mabye A possible way to make it transmit farther

author
t.rohner (author)2009-12-26

These types of oscillators are very unstable. There are better designs, which are only a little more complicated to build.
If it's your first transmitter, it's ok to play around with. (My first ones were of similar designs. That was at age 12, at age 17 i made my HAM license.)

But i don't think this one is of much practical use.

author
royshearer (author)t.rohner2010-04-30

Yeah the circuit is very unsophisticated, would love to improve it but do not have the know how. Can you suggest an better open alternative that would also fit into a similarly sized package (approx 27mm by 52mm board)?

author
t.rohner (author)royshearer2010-05-21

On this site you can find different schematics of basic transmitters.

http://www.zen22142.zen.co.uk/Circuits/rf/lrfmtx.htm
or the main rf-page
http://www.zen22142.zen.co.uk/Circuits/rf/rf.html

The first circuit uses a capacitive diode for modulation, where your design uses the the varying capacity of the transistor for modulation. Secondly, there is a amplifying stage, which not only amplifies the rf, but also decouples the oscillator a little bit from the antenna.
But if you want something real stable, you need a crystal-controlled oscillator or a PLL circuit. These designs are much more complicated, but lately you find these small transmitters for feeding your mp3-player sound to your car stereo via FM-radio. So there are definitely some highly integrated circuits to do this in such a small size.(maybe it's easier to buy one of them, but then it's not home-brewed...)

author
hitachi8 (author)2010-03-01

what is the Trimmer Cap ? UF ? 

author
Beduk (author)hitachi82010-04-30

I dont know what a trimmer cap is.uf stands for microfarad

author
hitachi8 (author)Beduk2010-04-30

i know , i was just asking for the capacity .
exemple : 20 UF  

author
royshearer (author)hitachi82010-03-03

Apologies, that should be a 4.2- 20pf Trimmer capacitor or similar

author
royshearer (author)royshearer2010-03-03

Have updated parts list to 0.24.1 accordingly

author
hitachi8 (author)royshearer2010-03-03

Thank you , 

author
engr.tahir (author)2010-03-26

 Hello! plz tell me how much area it covers???

author
royshearer (author)engr.tahir2010-03-26

so far seems to be 6m - 20m depending on the environment.

author
oc80 (author)2010-03-25

could you use 12 volt instead of 9?

author
royshearer (author)oc802010-03-26

I've not tried that, but its a sensitive circuit so I doubt it.

author
spacetarget (author)2010-01-29

Good work! I like the simple board layout.  This is a great low parts count transmitter.  Yes, the more parts the more stable, but the whole idea here is simple and eazy. I have made a lot of these. Lots of fun.

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Bio: I am a freelance design engineer and drummer. My business site is at http://www.zero-waste.co.uk and is often concerned with appropriate technologies ... More »
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