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Compact DC Voltage and Current Sense PCB with Analog Output
Features

Description•New! Three Ideals ranges for small robotics applications:o New 50 V / 180 Amps
o50 V / 90 Amps1
o New 13.6 V / 45 Amps

•Low zero current offset and high sensitivity
Analog output scaled for 3.3V ADC
Self powered
Compact thin design (4 x 15 x 19mm)
Analog Voltage Outputs for Sensed Parameters:
o 50V/180A = 63.69mV / Volt 18.30mV / Amp
o 50V/90A = 63.69mV / Volt 36.60mV / Amp
o 13.6V/45A = 242.3mV / Volt 73.20mV / Amp

A small voltage and current sense
PCB. DC current is determined bymeasuring voltage drop across ashunt resistors then converted toanalog voltage output by theTexas
Instruments
INA-169.
Voltage sense is accomplished byscaling to 3.3V ADC range by aprecision resistor divider.

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New! Re-designed to accept direct solder connection with
Deans Ultra connectors

The current limit coincides withmaximum power rating of theshunt resistors.

Assembly
The PCB is supplied without leads or connectors. Care must be exercised in soldering,
though the pad sizes are large enough to accommodate 12 gauge heavy duty leads (seephotograph below). Smaller gauge leads may be easier to solder without creating shorts.
The sensed current path is from “In+” to “Out+”. It is important to completely flood thisconnection path through shunt resistors with solder, on both sides of the PCB. As-supplied,the PCB has some solder flooding in this area, but it is up to you to ensure this is maintained
after attachment of leads. The shunt resistors each have four terminals in a Kelvinconfiguration. Two terminals carry the shunt current load, and the other two terminals areused for the voltage drop monitor INA-169.
It is important that both shunt resistors carry equal current load for sensor accuracy. To
ensure equal current load, the solder pads have a large via holes through which the leads
must pass through then be flooded with solder. Pass the “In+” and “Out+” leads through thelarge via holes and solder flooded on top and bottom of the PCB. The “GND” pads also havea large via hole however large current does not flow through the PCB from the GND leads;
the PCB “GND” pad is merely a small current common GND connection. The large current
flow in GND is from one lead to the other through the pad and solder-flooded via hole itself.

Photo Tips for Soldering

AttoPilot International LLC, 20111

180 Amp Sensor – Recommended Lead Arrangement
For the 180 Amp sensor, it is recommended to use doubled pairs of 12 gauge wire, as shown
above.
AttoPilot International LLC, 2011
Figure 1 Schematic2

Connection to ADC and Use
There are three 0.1” spaced plated through holes labeled “GND”, “V” and “I”. V is the analog output
for voltage sensing, and I is analog output for current sensing. V and I are both relative to GND. You
may use this sensor directly with a 5V ADC, however some resolution will be lost relative to a 3.3V
12 bit ADC unless a higher bit ADC is used. For scaling factors refer to “Features” table at the top of
page 1 of this document.
The I analog output contains a 0.1uF bypass capacitor, but no series resistor. To complete an RCfilter into the ADC inputs, you may place a low value resistor between the ADC inputs and I output.
The V output has a resistance of 14.7kΩ between the sensed drain and analog output with 0.1 uF
bypass capacitor for an approximate bandwidth of 108 Hz, via the equation 1/(2πRC)The shunt resistors typically need no cooling airflow as the copper leads provide a facile pathway
for heat loss. Power dissipation by the shunt resistors is:
Dissipated Power = I2 x R
For the “90A” device R = 5x10-4 Ohms, power in Watts, and current in Amperes. The upper power
limit of each shunt is 2 Watts for a total of 4 Watts in their parallel configuration. The upper current
limit is computed by solving the equation above for I with R = 0.0005 Ohms and Power = 4 Watts. I= (4 Watts / 0.0005 Ohms)0.5 = 89.44 Amps. Max amps for “45A” “180A” parts below.

Absolute Maximum Ratings
Operating Temperature………………....-55 to +125 Centigrade
Voltage with 3.3V ADC…………….......-0.3V to 51.8V (upper limit set to not exceed 3.3V output)
Voltage with 5V ADC…………………..-0.3V to 60V (upper limit set to not exceed INA169 limit)
Current……………………………….….44.7 / 89.4 / 178.8 Amps (upper limit set by shunt resistor)

AttoPilot International LLC, 20113