Converting 7v DC to 7v AC at 50-60Hz

Btw. the radio had a transformer 220v AC > 7v AC the datasheet can be found at:

I would really appreciate any good suggestions on where to find a schematic for this circuit

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When you say "the radio had a transformer..." does that mean you removed
it?

JF

Hacked as in you don't mind it not working anymore if you continue?

What's the AC for?

Why not just put +12V on pin 20, and ground on pin 15?

Just my $0.02. Which ain't worth much... finance.yahoo.com

Michael

You don't.

You run it off batteries, and then build up a crystal oscillator and divider chain to send pulses to the actual clock that it will count and use to keep time.

You don't need AC to run the clock, after all the existing power supply is there to convert AC to the DC that the clock needs. You do need a source of 60Hz pulses so the clock has something to count, the AC line usually being used for that purpose.

So you look at the clock IC, the large one, and try to find a datasheet or at least pinout for the IC. Then from there, you can figure out where the DC goes to power the IC, and where it gets a sample of the AC line to "clock" the clock. That point will need to be connected to a source of pulses at the line frequency (which I guess may be 50Hz if you are talking about 240v AC line.

This sort of thing was common decades ago, when digital clock building was a big wave. Now, clocks have become so cheap nobody really does it.

You need to rethink your problem, or at least restate your problem. There has to be a reason for you wanting to run this off a battery, explain that and a solution is easier to derive. I'm assuming you want it for the clock, and not the radio, but that's an assumption.

Some clock radios have a 9v battery to keep it going when the power goes off, though I've never had one to know if they actually keep the clock ticking away, or just supply power so the current time isn't lost in a temporary power loss. If they keep ticking, then that's likely a better choice for your project, since you no longer need to supply the pulses for the clock IC. Then it would just be a matter of applying DC voltage from the battery to where the rectifier from the AC transformer hits the filter capacitor.

But, if it's the clock you need, then maybe find an alternative. I bought an LCD clock a decade ago for about five dollars, and when the button battery died, I wired in an AA battery, and it just runs forever. No alarm feature though. But more expensive LCD clocks do have an alarm feature, and with some work one could use that to turn something else on, if that's the point of this project.

I bought an "atomic clock" at a garage sale this spring for all of 2.00, so one has to have a good reason for modifying a clock radio for battery operation in order to make it worth doing the work.

Michael

you have an LM8560 (or similar) based digital alarm clock and need a two-phase precise-frequency AC to drive the display and timer ?

As I understand it those chips don't actually need the negative part of the AC (which makes your life easier) but they do need the frequency to be right (or they keep time very poorly)

MM5369 is a chip that can make the right frequency for you then you just need to feed the output to some transistors to provide an inverted signal and boost the current so it can drive your display

Bye. Jasen

The MM5369 has been obsolete for so long (20 years?) that National Semiconductor doesn't even list it as obsolete. Also, there were special versions like 100 Hz so if you find old stock, or surplus it may not be 60 Hz. Even companies like Jameco don't list the MM5369 any more.

A better choice would be a crystal & divider chain, but keep in mind that some clock chips wand a 50% duty cucle at 60 Hz. Digikey has a lot of suitable crystals. Fo instance, they have 60 kHz crystals starting at 72 cebts. Divide by 1000 and yo have 60 Hz.

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Thanks for all the great info! Achually my plan is as follows: Use the display of the clockradio for my arduino, showing values. The advantage is that the clockradio only will take up 3 digital pins to show values .xx:xx (hours and minutes)

The plan was to make the display light up and setting the alarm to the value i need to show (through a loop counting up to the value on hours and a reset and a loop)

This means i don't need the timing functions of the chip. Neither do i need the alarm or radio features..(I achually already snapped those parts off the print)

Thanks in advance. Stig

I just cheked the local electronics shop and they listed 1 in stock.

yeah, if you don't give them that half the display will be brighter than the other half

crystals starting

what's a good way to divide a crystal by 1000 with a 12-15V supply?

I was thinking 2.457600 Mhz / 40960 using a CD4040 to drive the crystal and divide by 4096 and a CD4018 to divide by 10 more and provide a 50% duty cycle.

Bye. Jasen

I wouldn't touch that on a bet. I never buy singles of obsolete parts.

You don't really understand the design, do you? Some of the dividers need a 50% duty cycle, or they don't work, at all.

crystals starting

Sigh. Use a 78L05 voltage regulator to power the oscilator & divider, and a single transistor amp for level conversion.

You do realize that the higher the crystal frequency, the more power the divider circuit uses, don't you?

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There are two kinds of people on this earth:
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Fair enough, by saying that I meant that my availability test was inadiquate. (by 'just' I meant 'merely')

that's a surprise! I'd not expect timing to be that critical at such a low frequency,

crystals starting

so what's a good way to divide a crystal by 1000. giving a 50% duty cycle?

512:488 might be close enough and you can get that using a CD4040 (or similar TTL ripple counter chip) and and an 8-input and gate, else if you need 50:50 you'll need a flip-flop too.

you're asking for a fair collection of parts...

yeah, but the LED display would use much more anyway

anyway the original poster only needs a simple RC oscillator driving a couple high-side transistor switches, as he's apparently not using the timebase.

Bye. Jasen

crystals starting

Divide by 500, followed by a divide by wo.

Not really. Maybe $2 worth of CMOS, a crystal a couple caps a 2 cent transistor and some nickle resistors. There are dual BCD counter ICs like the mc14518 will give a clean divide by 100 followed by a divide by five, and a divide by two, or use mc14040 and configure it to count to

500, then use a flip flop o divide by two.

I have seen oscilator modules that put out 60 Hz. Commodore used one in their SX-64 computer, and I have seen them in some old battery backed clocks.

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The first sign of insanity is denying that you\'re crazy.

resistors cost more than caps?

hmm, that 4518 looks like a CMOS part number :) 4018 can do the final divide by 10 and give a 50% duty cycle (saving the flip flop)

so you can drive the crystal from a transistor? I've not seen that done before.

The clocks I've seen just used R-C oscilators, maybe 50Hz modules were harder to get or my clocks were crap.

Bye. Jasen

2 cent y

sed one

d

How should i connect power to the ic of the clockradio if i just want the display to work, being able to set the hours and minutes. (using it to display other values i need to read out from my robotic devices) As earlier described i need to power it from a dc supply.

Hope you can give me some advice on this issue, thanks

Stig

you still haven't said what chip it uses, I'll assume "8560" because that seems to be the most popular one

build this: (view in courier font)

7V ----+------ | +-[18K]-------|--------+ | | | | +--------+ | | | | | | | . . . .|. . . . | +-[10K]---> Freq | | . VCC(8) . | | | | . . | | | +--RES(4) OUT(3)--+-----+-----+-----------> D1 | . LM555 . | +-------TH(6) DIS(7)--- | .---> D2 | . . | |/ +-------TR(2) CV(5)-- +--[560R]---| PN2222 100nF | . . |\\| or BC337 ===== . GND(1) . ~\\ | . . . .|. . . . | | | | +-------------+-----------------------------+-- | | ---+-- gnd

That should hit the ball park of 60Hz give approximately equal time on each output and accept sufficient current to drive your LED display

Freq goes to pin 25 and D1 and D2 connect to the display. if the display is too bright you may need to add some voltage drop by putting (for example) 3 or 4 1N4001 diodes in series on D1 and D2. (too bright will wear it out quiickly)

Bye. Jasen

=A0 =A0

=A0

=A0 =A0

-> Freq

=A0 |

=A0

=A0

=A0 .---> D2

=A0 =A0 =A0 =A0 |/ =A0 =A0 =A0 =A0 =A0 =A0 =A0

222

=A0 =A0 =A0 |\\| or BC337 =A0 =A0 =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0 =A0 =A0~\\ =A0 =A0 =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0

hi Jasen,

Thanks for the schematics, It is an 8560 here is the datasheet, >

I don't find an lm555 just here in my pile of electronics, but i'd like to ask if its nessecary to generate a frequency if i just need the display to show me values given by sensors through my arduino. The idea was to just use the chip to control the display saving some pins on my arduino.

(sorry to be such a newbie)

In case i could hook it directly to the arduino with an external power of 7v dc could i then just give let in 7v to pin 15 or and 20 (Vss, Vdd)?

Stig

you need to generate a frequency, it doesn't need to be a precise or even predictable frequency, anything between 30 and 100Hz is probably fine, there is an aesthetic requirement is that it should be approximately symmetrical.

the chip only drives half the display at a time, you need some way to switch halves rapidly enough to see the complete display.

the chip would not run, it need some sort of clock signal to be able to measure how long the button inputs are active for, and to tell it which LEDs its output pins will drive. (you see that pins 1 to 13 each drive

2 segments of the display depending on which half-cycle the AC supply is in.)

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Bye.
   Jasen