Relay board not working

[roflkebab]

Hello

im having a problem with my home made relay board and the problem is i cant get that relay pull

board is pretty much like this one founded from google-> http://3.bp.blogspot.com/-010escsTmXk/U ... ircuit.gif

wires come to the board from top right 5V, two pins below Gnd and sixth from top on left side Gpio 17

components im now using (after propably twenty changes) are:
Meisei PS-5 relay
BC 237 transistor
2,6k resistor
and some random diode

after relay there is computer fan with 4,5V battery supply

raspberry pi's power supply is 1000mA

im commanding gpio's with wiring pi's commands
gpio mode 0 out
gpio write 0 1
gpio write 0 0

i hope someone could help me with this! maybe i just have screwd my relay board or those components are just wrong(im pretty newbie with components with voltage under 230~) or my awesome coding skills aint enough for raspberry or could it be my raspberry is broken or something??

Thanks!

[Tage]

the relay has 178ohm coil resistance and needs 3.8V to pick up. this is about 25mA. the transistor does not have much current gain, so you need to decrease the resistor value to perhaps 1k...1.5k
other than that, not much. measure the voltage across the coil and make sure it is higher than the pickup voltage when you apply current to the base. you did connect the emitter to GND of the Pi and Gnd of the 4.5V supply, right?
and never try to use this relay with 230Vac, please..

[gmc]

Do you have a multimeter?

When the GPIO pin goes high, measure the voltage at the collector on the transistor. Does it drop to 0v? (Or close to it?)

[roflkebab]

Thanks alot for replies!

if i remember right i tried to drop that resistance from 3k to some 500 ohms with potentiometer with no luck

emitter is connected to pi's gnd and that battery is not.
and yes im not gonna use this relay to connect 230vac if i do that i will use some bigger relays between these and vac

i will keep testing and tryin today and reply back then!

but first i will test if those relays will pull with my new mcp23017 and uln2803a boards that i put together yesterday^^
still need to solder few wires and and pins because i forgot to buy those jumper wires... those would have been much easier way i think and much less messy:D

im so exited to get back soldering and testing... cant sleep before i get those relays pullin with click from my laptop!

have a nice day!!

[roflkebab]

i really feel my self an idiot-.-

only needed to swap + and - on relays coil