K8048: Supply voltage should be >= 15V

Kits Microcontroller Programmer - Experimenting Project
1

Hi,

I see there are a lot of discussions about the power to be connected to the K8048 board. As far as I can see out of the electrical diagram, the input voltage should be minimal 15 Volts.

The reasoning behind this: VR1 is supposed to give an output voltage (Vpp) of 13.2V! (12 V + 0.6 + 0.6). This can only be achieved if its input voltage is above 14.3V (probably even a little higher). Furthermore, there is a voltage drop over D1 of about 0.7 Volts. This makes the minimum input voltage 14.3 + 0.7 V = 15 Volts. If this is not the case, then the “Vpp” will be too low. I do not know if this is a huge problem, but anyway, it is not according spec.

On the printed circuit board is indicated “15V DC adapter” and this seems to be OK.

I see that Velleman suggests, as power source, a non regulated adapter of 12V or 15V. I assume this type of adapters deliver a minimum of 15V? (I hope so, I assume the voltage outputted is meant to be fed into a regulator that outputs in turn 12V or 15V).

If using a “regulated” adapter, then a 12V one is not good (see the calculation above), only a 15V (or a little bit more) one.

2

As another user I would say that I think your reasoning is correct. I have previously said the same thing in these forums.

I think 12v is sufficient to RUN code once it is in a chip, but that 15v is needed to reliably program a chip. (But depending on the target chip and its circuit, sometimes it is possible to get lucky and get a good write with only a 12v supply.)