Remote-processing RPC-220 Manual de usuario descargar pdf (Pagina 43)

EXPANSION PORT SECTION 14

Page 14-1

Figure 14-1 Power Input, Jumper, and

Expansion Connectors

EXPANSION PORT AND POWER SECTION 14

INTRODUCTION

Expansion port at J2 allows you to connect other I/O

type cards for expanded capability. Power connector P1

is for ground, + 5, and higher voltage inputs.

EXPANSION PORT

Keep the connector length between J2 and expansion

card connectors as short as possible (4 inches or less).

Power and ground are available at this connector. Since

the ribbon cable is small gauge and has high resistance,

keep power currents as low as possible (less than 100

ma) to prevent ground loop problems. Ground loop

problems m anifest themselves as random resets, lockups,

and inaccurate A-D readings.

J2 expansion port pin out is sh own at the end of this

chapter.

EXTERNAL POWER

The RPC-220 accepts different voltage ranges,

depending upon the card. Recom mended operating

voltage is 5 ±0.25V, and is standard for all cards.

Absolute maxim um "5 volt" supply to the card is 6 volts.

This means you can hook up 4 ni-cad, carbon-zinc, or

alkaline batter ies to the 5 volt input.

Higher voltages are applied to the 'V' terminal on P1.

Jumper W4 to connect regulator output to the rest of the

card. External voltages of 6 to 16 volts are for P/N's

1715 and 1720. 5. 4 to 21 volts apply to P/N 1710 only.

Higher voltages may be applied provided a heat sink

under U10 is used. See "Heat Sink" below . Operating

current is 100 ma for the low power board (P/N 1710)

and 160 ma for others.

Board + 5 and gro und are applied through appr opriate

pins at J2, J3, J4 or P1.

P/N 1710 h as rever se voltage pr otection if pow er is

applied to externally. The board itself does not have 5V

reverse protection.

The maximum external voltage of 16 or 21 volts is due

to regulator power dissipation (see "Heat Sink" below).

Up to 30 volts may be applied if an adequate heat sink is

used under voltage regulator U10. The voltage may be

stepped down from higher voltages yet (up to 40 volts)

by putting a regulator (such as a 7824) to P1.

Depending upon the external voltage, you may need a

heat sink on the extra regulator.

Heat Sink

A heat sink under U10 is normally not necessary.

Conditions when you need a heat sink depend upon the

amount of power you expect U10 to dissipate and

ambient temperature.

First step is to determ ine the power you expect U10 to

dissipate. This is calculated as follows:

P(MAX) = (V

BATT

- 5) * I

Where: V

BATT

is battery or supply voltage

I = current into the board.

Current into the board depends upon its model number.

Use 100 ma for P/ N 1710 and 170 m a for all others.

Don' t forget to add current for other devices connected

to the bus, I/O ports, LC D display, and if you are taking

power from the regula ted output.

No heat sink is necessary if power( P (MAX ) ) is less

than 1.6W and the board oper ates at 25°C. T his means a

21 volt supply can be used with P/N 1710 and 14 volts

with all other models (assuming no additional cur rent is

used).

There is a small heat sink on the RPC-220. In marginal

situations, you can screw down U10 to the board to get

slightly better heat dissipation.

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