DIY Audio Projects Forum

DIY Crank Radio with TA7642

Hello radio friends,

because of the bad events in the world and the shocking pictures from Japan and Libya, I was in a small craft project hid. However, it is pure coincidence that this is a small emergency radio too. The craft work I used as a consolation prize and I have quarreled something, given the dramatic conditions, have fun DIY at present. Actually, this was supposed to be a funny post. But what's funny ... in such times.

I hope you also enthusiasm for these subsequent trace Radio.


It concerns with the device is a DIY-crank radio that instead of a battery that has a gold cap of 1F to store energy. This has the advantage that the 1F capacitor is charged in only thirty seconds and the radio for a playing time of about 1h, has enough energy.
Crank, gearbox and generator are from an old play box for children.
The output voltage of the generator is not more as 2VDC. To decouple, I chose a schottky diode, the voltage drop as low as possible to Keep The normal operating voltage is between 1 to 1.7 VDC. In order to this low voltage and low current of only about 100-250 uA to build good radio to be able, I chose the AM-TA7642 chip.
(Hi Ben )

The large ferrite antenna is captured sufficiently HF, there is no
extern grounding and also a port for a long wire antenna installed.
Also, a volume control is not necessary, although a local station, with a fully charged
Capacitor, can be somewhat annoying. Pivoting of the ferrite antenna is usually
already enough to vote .... otherwise a little off. The ferrite antenna is on
such a simple radio a good resource to strong stations hide
and thus achieve amazing results with good separation efficiency.


The fascinating thing about this technique is the absolute battery and battery-free operation.
Low mechanical energy is converted and can the radio, even after many
Years ago, now make it operational.

A radio with gears!

Greetings
Joe

Hi together,

here are the figures of the electrical data TA7642.

Remember .... at 6V it breaks. Therefore, the surge protection on the plan. For gold cap and chip 2x silicon diode at 0.6 V (selected) and a Schottky diode with 0.3 V and 20ohms in series with resistance.

joe

Hi Joe, great build! Can't say I have seen a DIY crank radio before.

Cheers

_________________
[ DIY Mains AC Power Cable Cord ] - [ K-12 Tube Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]

Gio,

yes the crank radio is a nice little toy. I have modified the surge protector and a red LED is now installed (1.6 volts). If the gold cap is charged to 1.6 V, it starts to light up. And now, you can also see that the radio is ready to start.


My next project is a little solarradio also with TA7642. But there is a problem.
MW at night is most interesting. More stations but unfortunately no sun.

Perhaps even more capacity? .... 5F !
Or more voltage and control the current.

Let's see ..
Greetings

Joe

Hi Joe,

very nice! Tell me about the 100k resistor, is this for some feedback? What does it do? Does it help selectivity?

Kind regards from Holland
Benny

_________________
Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project

Hi Ben,
So ...I will try it.
Please look first to your nice post "TA7642 alias MK484 alias ZN414i" There is the datasheed of TA7642. On Pin 2 you need a pre- voltage, for the base of the transistor T1. This 100k resistance
is also include in your circuit diagram in this post. It looks like only a little bit different. You get more selectivity with a tapped main coil. Maybe at 1/3 windings from ground.

Nice that you are back to DIY.

Best Greetings

Joe

Interesting diagram! I will look forward for the 1F capacitor.Also for the mechanics.Shall I use a motor from a toy?I know that when you rotate its rotor it can flash a LED (2...3V I think it can deliver)

I think that a small stepper motor would work better

it can deliver higher currents at lowwer rpm you would just need more diodes to rectifie it

if more voltage is needed you could just use a simple voltage multiplyer using caps and diodes

Nice project ben

Hello radiofriends,

the goldcap 1F on the picture above, has a maximum voltage value
of 2.5VDC. To rectifie the voltage down to 2.5V/1.6V, you can also use
silicon diodes (0.6V) and schottky diodes (0.3V).
Don´t use zener diodes, the leakage current is too high for the capacitor!
But to rectifie only the generator voltage it is ok

The normal operating voltage TA7642 is 1.1V - 1.6V.
"Shall I use a motor from a toy" Why not ? My small generator is
also a toy. A solarpanel it´s also possible. Sometimes you can find
goldcaps in old bicycle parking lights, or you buy it in a normal, commercial
electonic shop.

Have fun

Joe

Hi,again.I tryed with a motor from a CD-ROM and it run.I used a Ge Diode and a red led.But i cannot find 1F so I used for a test 10.000uF/16V..it run about 40sec on a weak/medium signal station,but on strong..about 1-2mins..hardly I can find but very expensive(in Romania about 200RON which means about 70$ or 50Eur)and with big dimensions Can you help me to find one..at..about 6V?Maybe it would be cheaper :-<