This is just another clock project. The processor that I am using here is PIC16F628A. Clock timing is very accurate thanks to RomanBlack Zero-error 1 second timer algorithm.
I've noticed that some of the tracks don't go anywhere: were they drawn by mistake and removed after the PCB was etched?
It looks like an interesting method of doing a silk screen. Have you tried toner transferring the silk screen and covering with a lay of conformal coating to give a black silk screen?
I'm talking about using the toner transfer process to put the silk screen directly on to the PCB so you don't have to mess around printing it on paper and gluing it to the board.
Once I've done the toner transfer, I cover it with a layer for conformal coating.
The PCB remains its natural colour and the silk screen is black, see attached.
Really nice clock. Just my 2c on clocks I would always use a crystal either 32,768kHz (common watch crystal) or something that divides easily in binary. Another trick is use the mains frequency, in most countries it's an extremely accurate timebase thus no crystal needed.
How hot does that 7805 get when you put 16 volts (full wave rectified 12VAC) into it, I would think it might need a heatsink.
I don't see any digit driving transistors or LED segment current limiting resistors, why did you decide not to include them? The ancient Microchip 16C84 clock app note doubled up some output pins to gain more current. The Mondo Superprobe also avoided resistors but claimed it worked because only one segment is ever driven at any moment.
Looks very professional. Are you planning to sell them as kits?
PS just a sidethought the 16F628A has the very flexible TMR2 special mode, it might be possible to use it as a 1 s or 0.5 s timebase without the fancy Roman Black 1 second fix.
Really nice clock. Just my 2c on clocks I would always use a crystal either 32,768kHz (common watch crystal) or something that divides easily in binary. Another trick is use the mains frequency, in most countries it's an extremely accurate timebase thus no crystal needed.
How hot does that 7805 get when you put 16 volts (full wave rectified 12VAC) into it, I would think it might need a heatsink.
I don't see any digit driving transistors or LED segment current limiting resistors, why did you decide not to include them? The ancient Microchip 16C84 clock app note doubled up some output pins to gain more current. The Mondo Superprobe also avoided resistors but claimed it worked because only one segment is ever driven at any moment.
Looks very professional. Are you planning to sell them as kits?
PS just a sidethought the 16F628A has the very flexible TMR2 special mode, it might be possible to use it as a 1 s or 0.5 s timebase without the fancy Roman Black 1 second fix.
hi,
As I understand it, the 1second accuracy obtained by using software will not correct for any drift in the frequency of the crystal itself.
Programming tweaking only sets the program timing to precisely 1 second at a particular crystal frequency.
If the crystal frequency drifts due to say ambient temperature changes so will the 1 second period.???
I was talking about the tracks pointed to in the following attachment.
Maybe its the filling algorithm going overboard?
It's no problem on a digital board like this, unless it's part of a crystal oscillator but it could be a problem if the track carries an op-amp's inputs which are a very small signal.
Thanks Hero, about the fillers i only use them for Ground or Power Planes also some times just stand alone copper blobs, keeps etching time to a minimum. I guess they will cause problems when doing wireless but never got the opportunity to do so. Tracks are supposed to left alone.
Another thing, I notice you've used some acute angles which isn't good practise because it can cause problems with etching. You might think I'm being picky and it is true that with the track thickness you've used it's unlikely to cause any problems but it's good to get into the habit of avoiding acute angle, so you won't run into any problems if/when you do use thinner tracks.
I've highlighted a few acute angles and some obtuse angles, which are bad and good respectively. There are a many more acute and obtuse angles on your board, I've just shown a few to give you the general idea.
Actually the brightness is even. I tried it with few types of SSDs. I didn't see any brightness varying. But the green colour SSD brightness level is little lower than the red. But not with each segment.