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The following picture shows the different connectors and important parts composing Jaluino Medium.
Several power sources options are available, selectable using jumpers. Fuse protection (500mA) helps keeping board safe when handled by distracted users...
PIC 18F4550 is clocked by a 20MHz crystal, allowing speed up to 48MHz using PLL (kind of black magic...).
Most used communication protocols are available from the board: USB, serial, I²C, ICSP. Those connectors are right angle male connectors, so easily plug wires and buses.
Resetting PIC 18F4550 can be done manually, using Reset push button, or using special RTS serial line, without manual intervention. This Reset-via-RTS feature is enabled using a jumper.
Finally, female connectors on the center compose shield connectors, used to expose pins to daughter boards.
See Hardware setup for detailed instructions about using jumpers and enabling/disabling features.
Board and shield sizes
Jaluino Medium board size is rather bigger than Arduino Duemilanove board. This is mainly because microntroller itself is bigger (it has more pins). Jaluino board is also single sided, to be easier to build at home. Finally, Jaluino provides more features, like a serial connector1 and an I²C connector.
Jaluino shield aera is smaller than the board itself, whereas Arduino's shield have quite the same size as the board.
|Length||4.53" (or 11.5cm)|
|Width||3.35" (or 8.5cm)|
|Length||3.35" (or 8.5cm)|
|Width||2.95" (or 7.5cm)|
Exposed pins through shield connectors
The following diagram shows 18F4550 pin layout, beside Jaluino shield connector. This is an important diagram, as it shows relation between PIC's pins and connectors, which pins is exposed2, which is not.
Jaluino Medium also exposes its pins as arbitrary number, following connect J1 to J4. Pins can then be accessed within code as number is necessary.
Power and voltages specifications
- AC/DC adaptor, usually delivering up to 24V. Input voltage must be at least 7Vac or 9Vdc with a maximum of 18Vac or 24Vdc depending on power consumption in your 5V and thus also 3.3V circuit.
- USB, power is directly taken from USB connector. USB outputs 5V and can deliver 100mA normaly or in special orcasions up to 500mA.
- serial module, where such modules can also provide power (like a USB-to-serial module). Like USB, serial module has to outputs 5V.
The maximum input current drawn by your 5V and 3.3V circuit depends on input voltage and also if you cool your voltage regulator (MC7805C only necessary).
If you don't cool your voltage regulator you have to look into the specs of your regulator at the therminal resistance, junction to ambient value. For the MC7805 this is 65°C/Watt.
This means that the temperature of your regulator increases 65°C with every 1Watt it consumes. If you add the ambiant temperature of aprox 25°C, your regulator will have an total temperature of 90°C after only consuming 1 Watt.
Although 90°C is not its limitation (the max temperature is 125°C), it warms enough to burn your fingers so lets stay below 1 watt consumption in your regulator.
Power = current x voltage, which gives W=I x U, so with this formula you can calculate your max current consumption in your 5V and 3.3V circuit.
For instance if you use a 9Vdc power supply voltage drop over the regulator is 9V - 1V (drop over bridge) - 5V = 3V.
Max current = W/U = 1/3 = 0.33A (total current in your 5V and thus also 3.3V circuit)
As a result of this, you can understand that if you need much current, it is always best to keep your input voltage as close as possible to the minimum input (9Vdc). If you only have a higher voltage power supply you need to limit your current, or power your board with USB.
If, for any reason, you need more power in your 5V and 3.3V circuit, you need to cool your 5V regulator. In this case you need a very well stabilized 9Vdc power Supply. you can than remove C6 (470uF/35V) which is only necessary for unstabilized or AC voltage input. Use this space to place a heatsink on 5V regulator (U2). (TODO: link to an appendix page explaining this modification, and add picture(s))
Jaluino Medium can provides three voltages on-board, Vin (only when using AC/DC adaptor on jack), 5V and 3.3V:
- Vin : voltage is voltage from DC adaptor minus 1V dropout voltage over bridge (DB1) or voltage from AC adapter multiplied with square root of 2 minus 1V dropout voltage over bridge (DB1).
- 5V : when using AC/DC adaptor, input voltage is regulated by 7805. This component outputs regulated 5V, which is a typical voltage used to power a microcontroller such as PIC 18F4550. When using USB or serial as power sources, no 5V regulation is done: this means there should be 5V as output (USB outputs 5V, if you use your serial module to power the board, make sure it outputs 5V).
- 3.3V : whatever the power sources, another voltage regulator produces 3.3V from 5V. Jaluino Medium makes your life easier and provides this common voltage, which is sometime used by some specific components.
Jaluino Medium version a and version b
Version a: this version uses pin layout Ground/Output/Input.Figure 5. 3.3V regulator pin layout for version a
The following components use this pin layout, and can be used to build Jaluino Medium version a: LD1117V33, LM1117T, LM1086.
Version b: this version uses pin layout Input/Ground/Ouput.Figure 6. 3.3V regulator pin layout for version b
The following components use this pin layout, and can be used to build Jaluino Medium version b: LM3940, LF33V.
Choosing version a or version b really is just about selecting which regulator you mostly can find, at lowest price. Other Jaluino features remain the same.