The CodeĬompared to the hardware assembling effort, the code is really simple stuff and the Arduino IDE makes it even simpler. The net effect of the relay 1, 2 states on the heater is summarized by the below table: RELAY 1īy contrast, the fan acts independently, controlled by the relay 3. Picture 9 - Fragment of the schematic showing the connections of the relays with the resistors Spreading the HeatĪ 5 V suction fan, borrowed from one of my Raspberry Pi's enclosures, is used to spread the heat, with the air flow directed as shown in the functional block (picture 2). It is worth nothing that, in stage 2 configuration, the power exceeds the nominal one of the resistors. The two-stages heating is achieved using, with the same supply voltage, 5 V, alternatively with the series of the 3 resistors (stage 1), or the series of two resistors (stage 2). I have used my laboratory DC power supply, able to provide up to 3 A current and another 'glorious' piece of hardware, the cheap 8 relays board you had already admired in picture 1. Eventually one resistor was discarded in the definitive prototype (see Griff's remark at the bottom of the page).Īrduino can neither provide, nor handle such large currents, so both an external power supply and a relay board is necessary. Picture 5 - First heater version, with 4 Cement resistors.
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