Em 14/11/2011 02:59, Grant Tudor escreveu: > Issac, > > Should have mentioned the voltage was measured using a CRO so I guess the > resistance was about 1M ohm. > > Grant > > On Sun, Nov 13, 2011 at 10:43 PM, Isaac Marino Bavaresco < > isaacbavaresco@yahoo.com.br> wrote: OK, I understand now. The fact is that a current transformer is aimed to produce *current*. It is normally used with a resistor in parallel to convert the current to voltage. If measured open, very high voltages may appear between the terminals. Seems that it is not your case. So the efficiency of your CT is much lower than the ones I built. You could use an Op-Amp to amplify the voltage... Isaac > >> Try using a resistor with higher value. >> >> >> Isaac >> >> >> >> Em 13/11/2011 07:35, Grant Tudor escreveu: >>> Isaac, >>> >>> Found an old PSU and pulled out the ferrite core. I set up a 60W light >>> globe as a test rig. With 5 turns I got about 3mV peak to peak. 25 turn= s >>> produced about 100mV peak to peak. A bit less than I expected but the >>> concept works. I think I need to get a bit more voltage though - will t= ry >>> out a few more variations over the next few days. >>> >>> Grant >>> >>> On Sun, Nov 13, 2011 at 7:36 AM, Grant Tudor >> wrote: >>>> Isaac, >>>> >>>> Thanks - I will give that idea a try. I have some old PSUs in the shed >>>> somewhere...... >>>> >>>> Grant >>>> >>>> >>>>> A current transformer is also very simple to implement and won't wast= e >>>>> any power. >>>>> You can build your own with a toroidal ferrite core found in computer >>>>> PSUs (around 1cm diameter), some insulated wire (around 28AWG) and an >> 1k >>>>> resistor. >>>>> The main advantages are that it doesn't waste power and it provides >>>>> electrical isolation. >>>>> >>>>> Simply wrap four turns of wire in the toroidal core and connect its t= wo >>>>> ends to the resistor. Insert one wire that goes to the heater in the >>>>> toroid's hole (just one leg, not the two wires). >>>>> When current passes through the heater a sinusoidal voltage will appe= ar >>>>> between the two terminals of the resistor. It is easy to rectify and >>>>> filter it and feed to the MCU. >>>>> If the voltage is too low, simply use a resistor with higher value. >>>>> >>>>> >>>>> Best regards, >>>>> >>>>> Isaac >>>>> >>>>> >>>>> -- >>>>> http://www.piclist.com PIC/SX FAQ & list archive >>>>> View/change your membership options at >>>>> http://mailman.mit.edu/mailman/listinfo/piclist >>>>> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .