hello i would like create an h bridge with relay. i have this relay http://www.te.com/catalog/pn/en/1419108-1 also i have 3.3kohm resistor and bc546 tranzistor because this relay is open with 12v and arduino is 5v. please help me. can you give a schematic for h bridge. the motor is 12dc volt and 1A.
You need a DPDT (Double Pole, Double Throw) relay to reverse a motor like an H-bridge. You can use two of those SPDT relays in place of one DPDT relay. You also need a second relay or a transistor to turn the motor on and off like an H-bridge. If your relay coil uses more than 40 mA or 5v you will need a transistor to drive the relay.
You might want to try an H-bridge chip like the L293:
Here is how you work out the relay switches.
Be careful that your control algorithm doesn't allow them to short out, as you would with transistors; be mindful that relays are slower than semiconductors.
With relays you can brake and coast.
0 1 2 3 Results
1 1 0 0 The motor will stop (brake)
1 0 1 0 The circuit will burn (smoke)
1 0 0 1 The motor will spin (forward)
0 1 1 0 The motor will spin (reverse)
0 1 0 1 The circuit will burn (smoke)
0 0 1 1 The motor will stop (brake)
0 0 0 0 The motor will coast (!!)
Hi, nothing will be burnable if you use two Single-Pole Double-throw relays with the motor connected to the COMMON (COM)terminals, + voltage to both NORMALLY OPEN (NO) terminals and - voltage to both NORMALLY CLOSED (NC) terminals.
If ONE relay is actuated, the motor will run one direction.
If the OTHER relay is actuated the motor will run in the other direction.
If NO relay or BOTH relays are actuated the motor will stop.
Here's a diagram from Mike Cook:
or you can use a relay board with drivers on it like the two-relay boards here: http://goo.gl/8ZEQ8
That circuit uses four (4) SPST relays. The relays coils are 5V and 10 mA which allows them to be driven directly from an Arduino output without a transistor driver.
That board has four SPDT relays with transistor drivers. You can control two motors with those four relays. The contacts on those relays are rated for DC30V at 10A so driving 12V 2A motors should not be a problem.
The H-Bridge%20relay.pdf circuit uses reed relays. They are neat because their coils can be energised with low current. The flip-side to that feature is that their contacts are not capable of switching large currents, < 1/2A.
To energise relays with bigger coils, and bigger contacts, you'll need a transistor.
You could run your motor with the reed relays, if you want to do some experimenting, but once the motor starts to do some work then it will probably roast (weld) the contacts of a reed relay.
The switching logic is still the same.
Kendall didn't make a very good schematic. I re-worked it a bit and have attached it. (If you're running the 12V motor, apply the +12V at the points labelled "+5".)