I found a post that describes the maximum current capability of pins on the various Picaxe chips here: http://www.picaxeforum.co.uk/showthread.php?11963-PICAXE-I-O-Current-Capability
However, in other posts I have found discussions of a maximum current at 20 milliamps instead of 25 milliamps.
At the moment I am interested in the 14M2, and I would like to drive this latching relay http://www.digikey.com/product-search/en/relays/signal-relays-up-to-2-amps/1049448?k=kemet+relay&k=&pkeyword=kemet+relay&pv675=3&pv72=1&pv1410=13&pv69=80&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25 directly from a Picaxe pin set high, using a capacitor on the low side of the relay coil to store energy to return the relay when the pin is set low.
The post above states that each pin can source or sink 25 milliamps, and this relay draws 20 milliamps at 5vdc (coil resistance = 250 ohms) only long enough to charge the capacitor. When the capacitor is charged, current draw drops dramatically and is no longer an issue. I expect the 20 milliamp draw will be very transitory.
Question I have is, is it safe in the long term to run this relay directly from the 14M2 pin? If 20ma is the maximum, this is working right at the edge, if it's 25ma, then I believe that is adequate headroom for this circuit.
If this isn't going to work I can go to a non-latching relay but I would prefer not to run 20ma continuously through the relay which will be mostly in a steady-state ON.
However, in other posts I have found discussions of a maximum current at 20 milliamps instead of 25 milliamps.
At the moment I am interested in the 14M2, and I would like to drive this latching relay http://www.digikey.com/product-search/en/relays/signal-relays-up-to-2-amps/1049448?k=kemet+relay&k=&pkeyword=kemet+relay&pv675=3&pv72=1&pv1410=13&pv69=80&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25 directly from a Picaxe pin set high, using a capacitor on the low side of the relay coil to store energy to return the relay when the pin is set low.
The post above states that each pin can source or sink 25 milliamps, and this relay draws 20 milliamps at 5vdc (coil resistance = 250 ohms) only long enough to charge the capacitor. When the capacitor is charged, current draw drops dramatically and is no longer an issue. I expect the 20 milliamp draw will be very transitory.
Question I have is, is it safe in the long term to run this relay directly from the 14M2 pin? If 20ma is the maximum, this is working right at the edge, if it's 25ma, then I believe that is adequate headroom for this circuit.
If this isn't going to work I can go to a non-latching relay but I would prefer not to run 20ma continuously through the relay which will be mostly in a steady-state ON.