For the 555 timer, a transformer is used to run the circuit, instead of the usual battery supply.
Although the transformer supplied the required 8-18 volts after regulation, the circuit will not work with it.
However, the circuit works ok with the 9v battery only.
Since the ac supply is necessary, I would appreciate some answers here.
Yours sincerely
Steve
constant DC?, does the voltage vary, does it drop below 6v often?
post a schematic (especially the supply, 555 circuit, and some indication of the load)
Bye. Jasen
I'll give this a go for you. Your AC needs to be rectified into DC to supply the 555, and smoothing the ripple with caps is a very good idea too. (its a timing chip) Then a regulator for a constant voltage, to say, 12 volts will also help greatly. If you need AC in your design too, then tap it from the transformer before the rectifier. Do further research!!
Mark
-- Transformer? Schematic? JF
what=92s the current draw on you secondary on your transformer and what is a 555 timer, they probably use a transformer because 9v b+ is not efficient to supply current over .5 milliamps and their would have to be some form of half wave rectification to convert to DC current transformers are much more efficient because the transformer passes as much current ether step up or step down as the circuit requires.
-- news:ubnfc45b5aoivlee9g9vb4rne4e5sgj54o@4ax.com JF
The rectified voltage does not vary, but is constant at the required
15 v.This is due to prior rectification with a couple of diodes and caps (1000 to 5000 uF).
Dc is sufficient to run the circuit ok, as provided by the 9 v battery.
Steve.
-- Got a schematic of the circuit you can post somewhere? JF
I have difficulty designing the circuit drawing in the gmail format here.
If somebody could refer to a free site, i'll put the schematic in the jpg/gif image.
Steve
Maybe Photobucket?
I have posted the schematic at
Please see.
Steve.
--- The top circuit is fine, and can be drawn in ASCII like this: (View in Courier)
+----+ 240AC>---+ +--|~ +|-----+----->VOUT P||S | | |+ R||E | | [4700µF] I||C | | | 240AC>---+ +--|~ -|-----+----->GND +----+The bottom circuit won't work because the transformer needs a center tap which needs to be grounded, like this:
240AC>---+ +----[DIODE>]--+ P||S | R||E--+-[-BFC+]---+ I||C | | 240AC>---+ +--|-[DIODE>]--+--->VOUT | +--------------->GNDI don't recall what your problem was; can you describe it again, please?
JF
The top one you drew will work, if you wired it correctly and used proper components. The DC voltage it produces is about 1.4 times the AC voltage produced at the secondary of the transformer. That DC voltage will drop lower when a load is connected to the supply.
You can regulate the DC voltage by adding a 3 leg regulator chip like an LM7809. See the datasheet fig 7 page 22 at
If that doesn't keep the voltage at a steady 9 volts, something is wrong with your transformer (undersized or defective) or your load draws excessive current.
Ed
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