Advice please on the SC8560 Clock IC

[ljcox]

I have attached the data sheet, see page 8.

The muxing is driven at the mains rate, ie. 50 Hz or 60 Hz so one pair of Displays is activated on one half cycle and the other pair on the other half cycle - called "cycle 1 & cycle 2" on the diagram. So far, so good.

But there must be a problem with the labelling of some of the pins in the diagrams. See page 8 for example.

1. Pin 3 is supposedly connected to "10's HR c & HR c" but pin 5 is connected to "HR c & d".

However, "HR c" can't be connected to both pins and since "HR e" is missing, one of the "HR c" must be meant to be "HR e".

2. But there is still a problem even if pin 5 is meant to connect to "HR d & e" since these pins can't be connected together.

3. The same applies to all of the other pins except pins 1, 2, 3, 10 & 14.

For example, pin 4 implies that "HR c" is connected to "HR d". This can't be true.

Does any one know the answer? (I don't have a clock to examine)

I expect that I could probably work it out if I spent enough time on it, but I don't want to "re-invent the wheel" if someone knows the answer.

Any advice will be appreciated

Also note that there is a minor error in the diagram on page 8.

If you number the diodes D1 ~ D4 from top to bottom, the cathode of D2 (shown connected to the junction of the 100 k & the 0.001 uF) is connected to the wrong point.

It should obviously be connected to the other end of the 100 k, ie. to the transformer secondary.

 

[mvs sarma]

Hi ljcox,

you have poits. there appears a printer's devil somewhere.
we have to search for updated info from manufacturer.
In the mean time, we have to acceprt that IC is workable and working also. your reply to Manoj , i agree , and i suugeted changes for disp drive also from the derived clock--it should work now even witha battery.

 

[nura100]

Hi!

here is the corrected Version of the circuit,
by the way SC8560 is Exact Copy of Sanyo's LM8560, Sanyo's Datasheet shows correct circuit, the Chinese Mfgr might have copied the original in a hurry.

arun

 

[mvs sarma]

Hi ljcox ,

neura100 brought us the reply but the diagram was different and aimed at pointing out mistake in the connection of diode before the 100K resistor-- for your point on HR c(e)at pin 3, please see the UTC8560 datasheet,

it is clear that pin 3 is 10's HR c & HR e. thus the printing mstake is resolved.
Reg item3 of your post, only one of the two pins siganl will be output relevent to cycle 1 or2 but not both at the same time.

elsewhere neura100 also indicated this problem, but he went a little ahead. pl see the relevent post

 

[ljcox]

Thanks for the feedback. I'll download the LM8560 or UTC8560 data sheet.

However, pin 3 is not the only issue to be resolved. I hope the other data sheets will be correct.

EDIT. I've downloaded both the Sanyo and UTC data sheets. One indicates that HR e is connected to pin 3 but the other has the same error.

However, I still cannot see how the other pin allocations can be correct. The data sheets all state that the displays are common cathode. But the only way that I can see that the pin allocations shown in the data sheets can be correct is if the cathodes are individual which seems very unlikely. Thus, using pin 6 as an example, the cathode of LED HR a would be connected to say Cycle 1 and the cathode of LED HR f would be connected to Cycle 2.

Anyway, this does not affect the main issue, ie. I can design the circuit without knowing how the pins are allocated.

What I need to know is voltage of winding w1 and the value of resistors R2 & R3 in the circuit posted by nura100 above.

 

[nura100]

Hello ljcox!

Trafo Details are as follows : Primary : 0-230VAC
Secondary:9-0-9 (18V C.T)
Resistors R2 & R3 : 300-460 Ohms*, 1 Watt
(*Used for Controlling Current Thru LEDS)

and No Individual Series Current Limiting resistors between Output Pins of Clock IC and Duplex Segments are needed.

nura

 

[ljcox]

Hello ljcox!

Trafo Details are as follows : Primary : 0-230VAC
Secondary:9-0-9 (18V C.T)
Resistors R2 & R3 : 300-460 Ohms*, 1 Watt
(*Used for Controlling Current Thru LEDS)

and No Individual Series Current Limiting resistors between Output Pins of Clock IC and Duplex Segments are needed.

nura

Thanks nura.