Not to nit-pick, but if you dont put a resistor on the base of that transistor the circuit may not work very long... (If you use a N-MOSFET you can get away with no resistor; plus you can drive larger loads without worrying about your transistor pulling more base current than your micro-controller can deliver)
The resistor value is very easily calculated: R = (Vsignal - 0.7) / (Irelay_coil / beta) Then round up to the nearest standard value. Beta is typically 100 (dont use that value directly in AC stuff, DC use only) Isaac Goldman 514-233-4423 This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. On Fri, Apr 15, 2016 at 11:29 AM, Frank Pittelli <[email protected]> wrote: > You probably won't find such a relay, but you can easily drive a 12v relay > coil from a 3.7v signal using a simple transistor, as shown in the attached > circuit. The specific transistor to be used depends on the max draw of the > relay coil, which is typically less than 1A for inexpensive 12V automotive > relays. The flyback diode shown in the circuit suppresses the > reverse-voltage electrical pulse generated by the relay coil when it is > deactivated. > > Best of all, transistors and diodes are cheap and they don't go boom if > you wire things wrong ... they just release some magic smoke. So, they are > perfect for teaching basic electronics and soldering. Add an inexpensive > indicator LED and resistor across the relay coil to add user feedback. > Replace the flyback diode by an LED (oriented opposite to the indicator > LED) and you can see the reverse-voltage electrical pulse when the relay > coil is deactivated. A perfect electro-mechanical project for beginners. > > On 4/15/2016 6:57 AM, 'neroc1' via R/C Tank Combat wrote: > >> I would still like to find a relay that has a coil operating at 3.7v >> that actuates a 12v circuit, just for simplicity >> > > -- > -- > You are currently subscribed to the "R/C Tank Combat" group. > To post a message, send email to [email protected] > To unsubscribe, send email to [email protected] > Visit the group at http://groups.google.com/group/rctankcombat > > --- You received this message because you are subscribed to the Google > Groups "R/C Tank Combat" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- -- You are currently subscribed to the "R/C Tank Combat" group. To post a message, send email to [email protected] To unsubscribe, send email to [email protected] Visit the group at http://groups.google.com/group/rctankcombat --- You received this message because you are subscribed to the Google Groups "R/C Tank Combat" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
