heatcoolnode

[{"id":"29f43b92.343e3c","type":"function","z":"6b333ae.0c170c4","name":"heat/cool","func":"\n/* A function designed to be used with node-red-contrib-pid in applications where both\n * heating and cooling are available to control the system.\n * The node is given a power value in msg.payload in the range 0 to 1, such as is produced by \n * node-red-contrib-pid and splits this into a heat power (o/p 1) and cool power (o/p 2) where\n * each is in the range 0 to 1.  These can then be fed directly into an output device, if this\n * is continuously variable, or they may be passed to node-red-contrib-timeprop nodes to generate\n * time proportioned on/off outputs.\n * There are two particular issues to be dealt with in a heat/cool application. Firstly is the fact\n * that the cooling device may be more or less powerful than the heating device. It is necessary\n * therefore to be able to adjust the gain of the system separately for heating and cooling. Secondly\n * is the highly non-linear response of some devices, notably refrigerant systems, that can have a\n * large effect initially, then this tails off. To compensate for this it is useful to have an \n * overlap range where both heat and cool are slightly on.\n *\n * To allow for these requirements two variables can be set below. The value of the power input value\n * where the heating starts to come on is determined by the variable heatMin.  Above this value the\n * heating will rise till it is fully on with an input of 1.\n * The cooling is fully on when value of the power input is 0, and falls till the cooling is fully\n * off at an input of coolMin.\n *\n * If the heating and cooling systems are of similar power then set heatMin and coolMin both to 0.5\n * in which case input values of 0.5 to 1.0 will map to heating outputs of 0.0 to 1.0,\n * and 0.5 down to 0.0 will map to cooling 0.0 to 1.0.\n * If, for example, the cooling system is more powerful than heating then they can both be set\n * to something like 0.7 which increases the gain in the heating region and reduces it\n * in the cooling region, to compensate for the different powers in the heating/cooling systems.\n * If some overlap is desired (so that both heat and cool are on slightly near the crossover\n * point) then overlap the two settings so that, for example, heatMin might be 0.45 and coolMin\n * might be 0.55\n */\n\nflow.set(String(msg.topic), Math. round(msg.payload*100))\n \n// set these as described above\nvar heatMin = 0.5;          // the value of input corresponding to 0 heat o/p\nvar coolMin = 0.5;          // the value of input corresponding to 0 cool o/p\n    \nvar power = msg.payload;\nvar heat = (power - heatMin)/(1 - heatMin);\n// limit to range 0 to 1\nheat = Math.min(Math.max(heat, 0), 1);\nvar cool = (coolMin - power) / coolMin;\n// limit to range 0 to 1\ncool = Math.min(Math.max(cool, 0), 1);\n\nmsg.payload = [{payload: heat}, {payload: cool}];\nreturn msg;\n","outputs":2,"noerr":0,"x":1680,"y":20,"wires":[[],[]]}]