Power I/O Wildcard User Guide
The Power I/O Wildcard provides eight high-current isolated MOSFET outputs and four high voltage isolated inputs. This tiny 2" by 2.5" module is a member of the Wildcard™ series that connects to Mosaic embedded controllers.
This document describes the capabilities of the Power I/O Wildcard, tells how to use and configure the hardware, shows how to read the inputs and write to the outputs, and presents complete schematics.
Power I/O Wildcard Hardware
The Power I/O Wildcard provides eight opto-isolated current-sinking outputs, and four opto-isolated high-voltage inputs. Jumpers enable module address selection and optional pull-up of the inputs. A Wildcard bus header connects to the host processor (e.g., QScreen or QCard Controller), and a field header brings out the isolated I/O signals. Table 1-1 provides specifications for the module’s inputs and outputs.
Specifications
Table 1-1 Power I/O Wildcard Specifications
| High Current DC Outputs (each channel, without heat sink, TA = 0 to 70°C) | |
|---|---|
| Output Channels: | 8 isolated current sinking outputs with common field supply and ground |
| MOSFET Used: | IRLZ14 NFET (60V 10A) (SSRS) |
| Isolation: | Optically isolated to ± 2500 V, 1011Ω isolation resistance |
| Output Protection: | Snub diodes to field supply to protect against inductive spikes |
| Field Voltage: | +4 to +50 VDC max |
| OFF Voltage: | +4 to +50 V (field supply) |
| OFF Leakage: | < 25 μA at 25° C |
| ON Voltage: | 0.6 V typical at 2 A continuously 0.3 V typical at 2 A intermittently |
| Max ON Resistance: | <0.2 Ω at I < 1A, typically 0.15 Ω <0.3 Ω to <0.4 Ω (at I = 2A for TA = 25 to 70°C) |
| Max ON Current: | 2 A continuously; or, 2 A pulses from 25 V at 50% duty cycle at frequencies to 5 kHz; or, 10 A pulse (<50 msec on time, <6% duty cycle at TA = 25°C or <4% duty cycle at TA = 70°C). |
| Switching Times: | ton = 9 μsec, toff = 12 μsec for 10%-90% transitions |
| Voltage / Switch Inputs (each channel) | |
|---|---|
| Input Channels: | 4 isolated bipolar voltage or switch closure inputs, with a common field ground and optional pull-ups to a common field supply |
| Input High Voltage: | ± 4 to ±50 VDC |
| Input Low Voltage: | < ± 0.8 V |
| Switch Inputs: | Optionally pulled-up through 10kΩ to field supply |
| Isolation: | Optically isolated to ± 2500 V, 1011Ω isolation resistance |
| Physical Specifications | |
|---|---|
| Current: |  mA |
| Weight: | 39 gram |
| Size: | 2" x 2.5" x 0.75" (50.8mm x 63.5mm x 19mm) |
Plugging in the Power I/O Wildcard
To connect the Power I/O Wildcard to a Mosaic Controller, follow these simple steps:
1. If using a Wildcard Carrier Board, connect the Wildcard Carrier Board (also known as the "Module Carrier Board") to the QED Board as outlined in the "Wildcard Carrier Board User Guide".
2. With the power off, connect the 24-pin Module Bus on the Power I/O Wildcard to Module Port 0 or Module Port 1 on a Wildcard Carrier Board, QScreen, PowerDock, QCard, or other Mosaic controller. The corner mounting holes on the module should line up with the standoffs on the Controller. The module ports are labeled on the silkscreen of the Controller. Note that the Power I/O Wildcard headers are configured to allow direct stacking onto a controller, even if other modules are also installed. Do not use ribbon cables to connect the Power I/O Wildcard to the controller. Use of ribbon cables on the Power I/O Wildcard’s field header is fine.
Selecting a Module Address
Once you have connected the Power I/O Wildcard to a controller, you must set the address of the module using jumper shunts across J1 and J2.
The Module Select Jumpers, labeled J1 and J2, select a 2-bit digital code that sets a unique address on the module port of the controller. Each module port accommodates up to 4 modules. Module Port 0 provides access to modules 0-3 while Module Port 1 provides access to modules 4-7. Two modules on the same port cannot have the same address (jumper settings). Table 1-2 shows the possible jumper settings and the corresponding addresses.
Table 1-2 Jumper Settings and Associated Addresses
| Wildcard Port | Wildcard Address | Installed Jumper Shunts |
|---|---|---|
| 0 | 0 | None |
| 1 | J1 | |
| 2 | J2 | |
| 3 | J1 and J2 | |
| 1 | 4 | None |
| 5 | J1 | |
| 6 | J2 | |
| 7 | J1 and J2 | |
| Note that address 0 is not available on the QScreen or Handheld. Use addresses 1 through 7 instead. | ||
Setting Outputs and Reading Inputs
Once the wildcard address is established by setting the jumpers on the Wildcard, you can output data to the high current outputs, or input data from the inputs simply by writing or reading a single byte (char) from hexadecimal offset 0x00 and 0x01 using IOStoreChar and IOFetchChar. For example, if the wildcard address is set to 3, you can set all the outputs simultaneously by storing the desired output byte to offset 0x00 on wildcard 3
IOStoreChar( desiredOutput, 0x00, 3 );
or read the inputs by fetching a byte from offset 0x01 on wildcard 03.
IOFetchChar( 0x01, 3 );
An output is turned ON, that is, set to a low-voltage, current-sinking output state by writing a one to the corresponding bit of the output byte at offset 0x00. To change only a single, or several, output lines without affecting the others use the software primitives IOSetBits, or IOClearBits as described in more detail later in this document.
Connecting High-Current Loads to the Outputs
The high current MOSFET outputs are opto-isolated to 2500 volts and capable of sinking 2 amps per channel continuously using field voltages up to 50 VDC at ambient temperatures to 70°C. The outputs are protected by snub diodes connected to the field supply to prevent damage from high-voltage inductive spikes. The MOSFET outputs control DC loads only. To control AC loads, use the AC Relay Wildcard, also available from Mosaic Industries.
Figure 1-1 shows how to connect a DC load (motor, solenoid, etc.) to the high current outputs. The field voltage supply, V+FieldOUT, can be as great as 50 VDC, and it must be at least 4 V to provide gate bias for the output MOSFETs.
If you test the MOSFET outputs, remember to connect a load to the output in order to see a voltage change as the output changes state. To perform simple non-isolated testing to verify the functionality of the board, connect a resistor (say, 1 kΩ) between the output and any convenient field supply (such as +5V) and connect the output’s field ground to the Ground connection of the +5V supply. Then, when an output bit is off, no current will flow in the load resistor, and a voltmeter or scope will show that its voltage is high (at +5V if you used this as the field supply). If you use the software from the software section of this document to turn an output bit on, current will flow through the output resistor, and your voltmeter or scope will show that the corresponding voltage falls to near zero.
The field connector on the Power I/O Wildcard is rated for continuous currents up to 2 amps and it should mate with a connector that is capable of carrying the required load current for your application. Note that standard insulation-displacement ribbon cable connectors are rated at only 1 amp per contact.
Figure 1-1 Connecting a DC load to a high current output.
Maximum Ratings: Current, Power and Switching Frequency
Without using heat sinks the outputs can each sink 2 A continuously. They can also sink pulses of greater current (up to 10 A) as long as the pulse duration and frequency do not cause a greater power dissipation than 2 A of continuous current does.
Owing to the low ON resistance of the MOSFETS the power dissipated in them is low: when OFF they are subjected to the field voltage but there is no current so no power is dissipated; when ON their internal resistance is low (typically 0.15 Ω) so the I2R power is also low.
Without a heat sink, the maximum electrical power allowed for each channel is limited by convection/conduction from the MOSFET’s TO-220 package, and depends on the ambient temperature, as shown in Equation 1-1. In the equation, Tjmax is the maximum junction temperature (175°C), TA is the ambient temperature (0-70°C), and RΘ is the junction to ambient thermal resistance (62 °C/W). For an ambient temperature increasing from 25°C to 70°C, the maximum power that can be dissipated decreases from 2.4 W to 1.7 W.
Max Power Dissipated = (Tjmax-TA)/RΘ Eqn. 1-1
The heat generated in the MOSFET comprises two terms, an I2R term and a frequency-dependent switching loss term, as given in Equation 1-2.
Power Generated = I2rds D + F I V (ton + toff)/(6 or 2) Eqn. 1-2
The first term is the product of the square of the ON current, the device resistance (rds = 0.4 Ω max at the max junction temperature), and the duty factor (0<D<1). The duty factor is the ratio of ON time to (ON + OFF) time if the channel is switched repeatedly. The duty factor is unity, (D=1), for continuous current. The second term represents switching loss incurred during the turn on and off transitions. It is the product of the frequency, F, the ON current and OFF voltage, I and V, and the sum of the ON and OFF transition times (21 μsec). There is either a 6 or a 2 in the denominator if switching resistive (use 6) or inductive (use 2) loads respectively. A load is considered inductive if its inductance , L, is greater than a threshold given by L > V toff /4I. For example, if I=2A and V=25V, the load is inductive if its inductance is greater than 25V * 12μsec / (4 * 2A) = 38 μH.
The conditions of maximum current, voltage and frequency are found by setting the maximum package dissipation equal to the electrical power as shown in Equation 1-3.
(Tjmax-TA)/RΘ = I2rds D + F I V (ton + toff)/(6 or 2) Eqn. 1-3
And substituting the appropriate constants, as,
(175-TA)/62 = 0.4 I2 D + 0.021 F I V / (6 or 2) Eqn. 1-4
in which I is in amps, V in volts, D is a fraction between 0 and 1, F is in kHz, and TA is in °C.
Equation 1-4 can be solved to find any of the parameters (I, V, D, F, TA) given the others.
Example 1, finding maximum DC current: For continuous DC current (F=0 and the channel is ON so D=1) and a maximum ambient temperature of TA=50°C, the maximum continuous current is found by solving Eqn. 1-4 to be 2.2 A. At the maximum specified ambient temperature, TA=70°C, the maximum current is found to be 2.06 A.
Example 2, finding a maximum switching frequency: For driving a 1 A resistive load (I=1) from a field supply of 25 volts (V=25) with a duty cycle of 50% (D=0.5) at a maximum ambient temperature of TA=70°C, we find a maximum frequency, F, of 17 kHz.
Example 3, finding a maximum switching frequency for an inductive load: For driving 1A into an inductive load (I=1) of 1 mH from a field supply of 25 volts (V=25) with a duty cycle of 50% (D=0.5) at a maximum ambient temperature of TA=70°C, we use the denominator of 2 in the above equation and find a maximum frequency, F, of 5.6 kHz.
Example 4, finding duty cycle: PWM modulation of a thermoelectric cooler requires driving 4 A into the cooler at its minimum recommended frequency of 1 kHz from a 12 volt supply. The instrument must operate at ambient temperatures up to 70°C. That is, I=4, F=1kHz, V=6, and TA=70°C. The maximum duty cycle is found as 24%.
Heat Sinking
While it is possible to heat sink the MOSFETS, because of the limited space between MOSFETs and the need to electrically insulate the heat sink from each MOSFET we do not recommend heat sinking. Even so, if you are careful and you do heat sink the MOSFET drivers the maximum ratings improve. In particular, one or two of the channels can be heat sunk with small free-standing TO-220 heat sinks. To determine the maximum ratings, the same equation may be used, but with the appropriate thermal resistance substituted for RΘ. To the heat sink thermal resistance (heat sink to ambient) you must always add the thermal resistance between the junction and the package of 3.5 °C/W, and the case to sink resistance, typically between 0.1 and 1.0 °C/W.
Small, free-standing heat sinks (0.5 x 0.5 x 0.75" heatsinks of 18.8 °C/W such as Digikey HS121-ND) can be used to decrease the thermal resistance from 62 to about 18.8+3.5+1.0 = 23.3 °C/W resulting in an increase in continuous current from 2A to 3.3A. The tabs of the TO-220 packages of the MOSFETs are not electrically isolated – they are connected to the drains (the outputs). Consequently, if the package is heat sunk the heat sink must be kept electrically insulated from the tabs, or it must be kept insulated from everything else.
Connecting to the Inputs
The high voltage inputs are also optically isolated to ±2500 volts and capable of sensing voltages of ±4 to ±50 VDC. Figure 1-2 illustrates how to connect an input voltage to the Power I/O Wildcard. When the input voltage is ±5 to ±50V, a logical 1 input will be read. When the input voltage is less than ±0.8V, a logical 0 input will be read.
Figure 1-2 Connecting a voltage to a high-voltage input.
Onboard pull-up resistors (labeled PU0 to PU3 on the Power I/O Wildcard silkscreen) allow you to monitor the state of a contact closure device such as a switch. The switch is connected as shown in Figure 1-3. For example, to interface a contact closure device to input channel IN1, install a jumper shunt across J5 and connect the contact closure device. The input is read as a logical 1 when the switch contact is open (contacts not connected), and it is read as a logical 0 when the device is closed (contacts connected). When the pull-up resistors are used, V+ Field IN must be in the range of ±4 to ±50VDC for proper operation.
Figure 1-3 Connecting a contact closure device such as a switch to the Power I/O Wildcard. To provide the proper voltage swing at the input, install a jumper shunt across J5. The input will be read as a logical 1 when the switch contact is open and as a logical 0 when the switch is closed.
Power I/O Wildcard Field Header
The isolated high voltage inputs and outputs are brought out to a 24-pin dual row header on the Power I/O Wildcard as shown in Table 1-3.
To connect your transducer signals or control inputs to the Field Bus (H3 on the Power I/O Wildcard) use a ribbon cable or the Screw Terminal Module that brings out the signals to screw terminal blocks. Remember that most ribbon cable connectors are rated at 1 amp per contact.
Table 1-3 Power I/O Wildcard Field Header
| Signal | Pins | Signal | |
|---|---|---|---|
| 0utput.GND | – 1 | 2 – | OUT7 |
| 0utput.GND | – 3 | 4 – | OUT6 |
| 0utput.GND | – 5 | 6 – | OUT5 |
| 0utput.GND | – 7 | 8 – | OUT4 |
| 0utput.GND | – 9 | 10 – | OUT3 |
| 0utput.GND | – 11 | 12 – | OUT2 |
| 0utput.GND | – 13 | 14 – | OUT1 |
| 0utput.GND | – 15 | 16 – | OUT0 |
| V+FieldOUT | – 17 | 18 – | IN3 |
| V+FieldIN | – 19 | 20 – | IN2 |
| Input.GND | – 21 | 22 – | IN1 |
| Input.GND | – 23 | 24 – | IN0 |
Software
To use the eight high current, isolated MOSFET outputs for instrumentation, use the software primitives IOStoreChar, IOChangeBits, IOSetBits, or IOClearBits (IO.C!, IO.CHANGE.BITS, IO.SET.BITS, or IO.CLEAR.BITS in FORTH). To read back the state of the eight outputs or the four inputs, use the software primitive IOFetchChar (IO.C@ in FORTH). The hexadecimal offsetof the output port is 0x00 and the offset address of the input port is 0x01. Code Listings 1-1 and 1-2 are demonstration programs that set, clear, and read the high current isolated outputs, they also have a function that reads the high voltage isolated inputs.
Listing 1-1 C Code to control the Power I/O Module.
The C demo is located in your installation directory. It is also provided here for your reference.
Listing 1-2 Forth Code to control the Power I/O Module.
The forth demo is located in your installation directory. It is also provided here for your reference.
