Inverter for soldering iron

Here is a simple but inexpensive
inverter for using a small
soldering iron (25W, 35W,
etc) in the absence of mains supply. It
uses eight transistors and a few resistors
and capacitors.
Transistors T1 and T2 (each BC547)
form an astable multivibrator that produces
50Hz signal. The complementary
outputs from the collectors of transistors
T1 and T2 are fed to pnp Darlington
driver stages formed by transistor
 Lovely T.P.
Inverter for Soldering Iron
s.c. dwivedi
pairs T3-T5 and T4-T6 (utilising BC558
and BD140). The outputs from the
drivers are fed to transistors T7 and T8
(each 2N3055) connected for push-pull
operation. Use suitable heat-sinks for
transistors T5 through T8.
A 230V AC primary to 12V-0-12V,
4.5A secondary transformer (X1) is
used. The centre-tapped terminal of
the secondary of the transformer is
connected to the battery (12V, 7Ah),
while the other two terminals of the
secondary are connected to the collectors
of power transistors T7 and T8,
respectively.
When you power the circuit using
switch S1, transformer X1 produces
230V AC at its primary terminal. This
voltage can be used to heat your soldering
iron.
Assemble the circuit on a generalpurpose
PCB and house in a suitable
cabinet. Connect the
battery and transformer
with suitable
current-carrying
wires. On the front
panel of the box, fit
power switch S1 and
a 3-pin socket for connecting
the soldering
iron.
Note that the ratings
of the battery,
transistors T7 and
T8, and transformer
may vary as these all
depend on the load
(soldering iron). 