| ??? 04/21/10 14:02 Read: times |
#175218 - answers Responding to: ???'s previous message |
In the circuit in Faq there are is one 2.2 K resistor between uc pin and base of PNP .
Also there is a 10 K resistor between 5V and base of PNP Finally the base of the NPN is grounded through a 2.2 K resistor. First, for circuits like this, most of us use 'grab bag' values thus either resistor value will be good. The base to emitter resistors are a good idea, they make the circuit more 'secure'. Also I forgot the flyback diode, do not do so. Will these three changes affect any of the functioning of the circuit? Also are the resistor values dependent on the final relay voltage? no and no What is the maximum current that this circuit can supply?Is it limited only by the supply of 5V supply? the voltage for (and connected to) the relay is only dependent on the voltage the NPN can handle. the current can be improved by replacing the NPN with a darlington, It is the_curremnt_through_the_NPN_base_resistor * NPN_min_beta *1/2 . 1/4 would be better than 1/2 it is a reduction to guarantee the transistor goes into saturation. Erik |
| Topic | Author | Date |
| solenoid driver | 01/01/70 00:00 | |
| switch on and off at high speed | 01/01/70 00:00 | |
| speed range | 01/01/70 00:00 | |
| the typical circuit | 01/01/70 00:00 | |
| clarification | 01/01/70 00:00 | |
| "ASCII schematic" | 01/01/70 00:00 | |
| ASCII schematic is useful!!! | 01/01/70 00:00 | |
| answers | 01/01/70 00:00 | |
| It's in the FAQ | 01/01/70 00:00 | |
| Thanks for the reference | 01/01/70 00:00 | |
| Have you considered a "solenoid driver"? | 01/01/70 00:00 | |
| Ready made solenoid drivers | 01/01/70 00:00 | |
| recognized my error | 01/01/70 00:00 | |
| This is not rocket-science | 01/01/70 00:00 | |
| Check the data sheet you linked... | 01/01/70 00:00 | |
Yes, people do have to read the datasheet | 01/01/70 00:00 | |
| re: solenoid driver | 01/01/70 00:00 |