User guide
LED
LED
+ve
A
B`
B``
-ve
+ve
A
B`
B``
-ve
+ve
A
B`
B``
-ve
+ve
A
B`
B``
-ve
+ve
A
B`
B``
-ve
+ve
A
B`
B``
-ve
NPN
PNP
S312 Series Interface Relays
These transistorised relays are designed as  general 
purpose interface   devices. Double pole   changeover 
contacts rated at 2A 30vdc 0.5A 120vac are provided. 
The circuit board also carries an LED to indicate when 
the relay coil is energised. The coil is suppressed 
against back emf and diode protection is given against 
reverse polarity.
There are three versions available for either 12 or 24v 
dc power.
S312 N / N24 uses a NPN transistor Fig 1
S312 P / P24 uses a PNP transistor Fig 2
S312 T / T24 as NPN with RC timing components Fig 1
A self adhesive backing is provided for rapid fixing or 
alternatively the four fixing holes  provided can be 
used.
In the examples 12vdc or 24vdc (Depending on 
version of product), should be applied 
permanently to the terminals marked +ve &  -ve
S312T additional
components
S312 P/P24 Applying a +ve signal greater 
than 8v to either B` or B`` will de-energise 
the relay. When both e signals are 
removed the relay will re-energise.
S312 N/N24  Applying a +ve signal 
greater than 4v (eg TTL) to either B` or 
B`` will energise the relay. When the 
signal is removed the coil will de-
energise.
S312 N/N24 Closing switch S will 
energise the relay. When switch S is 
opened the relay will de-energise.
S312 P/P24 Closing switch S will de-
energise the relay. When switch S is 
opened the relay will re-energise.
S312 N/N24 Closing switch S will de-
energise the relay. When switch S is 
opened the coil will energise.
S312 P/P24  Closing switch S will 
energise the relay. When switch S is 
opened the relay will de-energise.
S312 N/N24 connected as a latching relay. P1 and P2 are Normally Open 
pushbuttons. When P1 is pressed the relay will energise and remains energised. To 
de-energise the relay press P2
S312 T/T24  uses an NPN transistor and is fitted with additional components (see Fig 
1). When the switch S is closed the capacitor is charged almost immediately and the 
relay coil energises, If switch S is then opened the voltage across the capacitor falls 
and eventually the coil of the relay de-energises. The discharge period can be varied 
by the on board potentiometer. The delay that can be achieved is from a minimum of 
approximately 3 seconds to a maximum of 60 seconds. Do NOT connect B` or B`` to 
+ve. The contacts should be derated by 50% because of the slow release time. Hoyles 
Electronic Developments also manufacturer timers with better resetting accuracy and 
timing ranges up to 2 hours.
s
s
s
+ve
A
B`
B``
-ve
P1
P2
*
+
A
B`
B``
-
47 mm
52 mm
16 mm
Fig 1
Fig 2
Fig 3
Fig 4
Fig 5
Fig 8
Fig Fig 6
Fig 7
w:\Tech\S312 interface relays\Common\Installation Instructions\60071.cdr April 2010 Iss 3
LED
Pot
T. 01744 886600 F. 01744 886607 E. sales@hoyles.com W. www.hoyles.com
Hoyles Electronic Developments Ltd

