Shortstub,
i think i have solved my problem, at least i think so... i did the following:
1.) supplied a diode across NC and Common contact to supress incoming EMF current during 'turn-off'
2.) connected a 1 ohm resistor between relay and motor to limit the current during startup
3.)...
Wow so much replies since i last read this....
1.) Shortstub maybe right that switching rate is a problem since if i 'switch' the relay at lower rate, evreything works okay....
2.) i dont know if this will help, im using a SPDT relay, and looking at my schematic above, the motor's EMF during...
cbarn: ok ill do that. problem is the relays might already be busted, and i have to keep busting relays to see what value worksÜ
But i have to do it, got no other choice...
Shortstub:
1.) Yes, pin 9 is connected to the positive side of the relay.
2.) I think coil resistance is 63ohms
3.)...
cbarn: i will try thatÜ any recommendatin on the resistor value?
pete: yes switching fast means turning the motor on and off... as far as i know, DC motors have high transient currents, causing the 'melt'
i just read about the double break contacts, thankx to jbartos and crowbar, will also try...
Im having problems understanding the difference between mechanical binding and contact welding, wat i do know is that the contact or pin inside the relay that is supposed to switch, welds or binds to either the NO or NC pin.
This problem arises when i switch fast, which led me to conclude that...
the coils are controlled by the darlington array and a microcontroller, so when i send a signal to the coil of the relay, it should energize and switch the contacts... but mine does not(after quite some time), so i have to determine whether its the coil not getting enrgized or the contact not...
the darlington array is only used for the coil, which has a very minimal current and voltage....
i dont think there's anything wrong wiht the coil since it still produces the right voltage during switching, problem is contacts does not 'switch', which led me to conclude that it has welded to...
i'm not sure wats the difference between relay mechanical binding and relay contact welding, but wat im refering to is the contacts inside the relay does not respond to the applied coil voltage.
i think there is no problem with the coil voltage since it does work and when i take the voltage...
i dont know if it is a "novice" question, but what is a double break contacts?
also can u suggest on a better contact configuration?
another question is: is there any kind of ckt that i can use to protect or lessen the surge currents
thankx againÜ
CROWBAR: i think u rightÜ the relay stops switching when i deliberatly switch fast....
does oversizing mean higher contact rating?
no other solution? like supression ckts? if so, how do i connect them, im confused on the configuration of say, diodes polarity with respect to the contact
--->...
Thankx for everyone's reply...
anyway, relay is confirmed to be 28vdc, about the 10A inductive ill check that..Ü
Signals from darlington is confirmed to be correct, and reason i suggested it was welding because when i give it a hard tap (the relay) it workd fine again for a while...
also when...
Why does my relays stop "switching" after some time of use. I am currently working on controlling a 24v 5A DC motor using a microcontroller and a uln2003a darlington array. Also using a 5v coil rating, 28v contact rating, 10A relay to control the motor. Everything is working perfectly...
