Manual OC32/NG
VPEB
Control your Miniature World
Page 14 of 48
Version 1.0 – December 15
th
, 2017
2017 Leon van Perlo
4
Power Supplies
Fig 6: Connecting Power Supplies to the OC32/NG
4.1
General
Both the OC32 itself and the devices that the OC32 controls (e.g. signals, motors, relay’s)
obviously need a power supply to operate. In many cases you can use the same power supply
for the OC32 and the devices it controls.
Note that
any
power supply delivered to the OC32, be it for the OC32 itself or for the
controlled devices, must be a
positive DC
Voltage.
Attention: Connecting an AC voltage or reversing the + and – connections of a DC power
supply will inevitably result in a defect in the module that is beyond guarantee. Be sure
therefore about the kind of power supply you connect the OC32 to.
4.2
Some words about power supplies:
We often get the question if a model railroad transformer can be used for the OC32. Model
railroad transformers rarely provide a proper DC voltage. You can use them conveniently,
but with a some consideration and simple modification. More about that later on.
For less than €20,= already you can buy a properly stabilized, configurable, switching and
therefore economical DC power supply that can provide 2-3 Amps. This is more current than
an average model railroad transformer supplies, so think twice if it is worth the effort and
PWR
Sink 0..7
Source 0..7
Sink 16..23
Source 16..23
Sink 8..15
Source 8..15
Sink 24..31
Source 24..31
Power Jumper Jp1 (0..15)
K1
K5A
K5B
GND
GND
(2x)
Vp2
(2x)
GND
(2x)
Vp1
(2x)
Power Jumper Jp2 (16..23)
PWR
Sink 0..7
Source 0..7
Sink 16..23
Source 16..23
Sink 8..15
Source 8..15
Sink 24..31
Source 24..31
Power Jumper Jp1 (0..15)
K1
K5A
K5B
GND
GND
(2x)
Vp2
(2x)
GND
(2x)
Vp1
(2x)
Power Jumper Jp2 (16..23)
Control your Miniature World
VPEB
Manual OC32/NG
2017 Leon van Perlo
Version 1.0 – December 15
th
, 2017
Page 35 of 48
6.2
Multiple power-supplies, different voltages
Even in case you have several pieces of equipment which require different power voltages,
you can drive them from the same OC32. Multiple DC power supplies can be used
simultaneously.
First the OC32/NG has two separate power planes for driving loads. You can separate Vp1
and Vp2 and drive each section with it’s own power supply. This works for all drivers (sink,
source, ADM’s).
6.2.1
Multiple power-supplies using Sink-drivers
In addition to the fact that you have two power groups on the OC32/NG, when using Sink
Drivers the number of different power supplies is virtually unlimited. The load is connected
between the plus pole of the power supply and the output of the OC32 (Sink Driver). As long
as the minus pole of all power supplies are connected to each other and to the GND of the
OC32 the plus pole of each of those power supplies can be used to feed one or more
separate accessories. The plus pole of the load is connected to the plus pole of its power
supply while the minus pole of the load is connected to the output of the OC32.
There is however one additional point of interest:
In the Sink Drivers free-wheeling diodes are integrated to facilitate inductive loads to be
switched-off without damage, like solenoids or relays. These diodes reside between the
output (Anode) and Vp (Cathode). When using different power supplies, the consequence of
this is that
always the power supply providing the highest voltage in the Vp group shall
be connected to Vp
.
In most cases it is not desirable to use that highest voltage for the internal power of the
OC32 also. A lower power should by used to operate the OC32. To achieve that, PWR and
Vp have to be connected separately. The power jumper JP1/JP2 on the OC32 print has to be
removed. The highest voltage has to be connected to Vp. The lower voltage has to be
connected to PWR.
6.2.2
Multiple power-supplies using Source-drivers
Unlike the case when using Sink Drivers, it is not possible to connect more than one power
supply to the Source Drivers in one Vp group. The Source Driver obtains the power from Vp
and only one voltage can be connected to Vp.
When using both Source and Sink Drivers for different outputs but in the same Vp group it
is possible to use different power supplies as described in
6.2.1 above, but
the highest
voltage has to be connected to Vp, being the voltage used by the Source Driver.
All
devices driven by the source driver will be driven with the same and highest Voltage.
6.2.3
High power Voltage
The Sink and Source drivers can deliver/withstand up to 50V. It may not be wise to use such
a high voltage because this approaches the voltage levels that are harmful to the human
body when touched. More over in the miniature world there are hardly any devices requiring
such a high voltage.
If you need to use a voltage above 15V for your loads it is advisable to separate Vp and
PWR. If the voltage is higher than 25V the separation is mandatory because the voltage
stabilizer of the OC32 is not specified to handle more than 25V.
