Toggle Switch Pneumatic Control ~ Eko Sharing

Ditulis oleh : eko

Sunday, March 1, 2015

( Click picture for detail view )

Now i will share my project about pneumatic control using toggle switch system. It use to control movement of pneumatic to open and close. In this case, i use 24Vdc solenoide valve to control the pneumatic. I was applied this circuit to Rohde & Schwarz chamber test. In this circuit we use one switch to control the open close state. To select state of pneumatic we just push switch once and to toggle the state we just push the switch one more.

How It Works ?

To more easy, we group the circuit into small part. There is power supply, toggle switch, relay control and offcourse the limiter. Now lets study it one by one.

Power Supply

Because i use 24Vdc pneumatic control so we need 24Vdc supply. The circuit is look different then ordinary power supply. Yes, in the circuit above i use doubler circuit to multiply voltage twice from 12V to 24V. The reason is i use 12Vac output transformator.

The doubler circuit is build by Diode D14, D15 and Elco C5, C6. To stabilize output, we use IC 7824 (IC1) and C7. The latest part of the circuit is IC 7812 (IC2) and C8 to produce 12Vdc for toggle switch and relay supply.

Toggle Switch

Now we go to the main unit of the circuit, there is toggle switch control. This circuit is use to do the toggle state when we push the switch. The working principle of the circuit is when we push the switch once, circuit will latch ON state and when we pressed once more, circuit will toggle and latch OFF state.

The circuit of toggle switch control is build by two transistor T1 and T2. When supply through to the circuit at the first time, T2 will ON because the current that flow to the base T2 is greater than base T1. When T2 state is ON, collector T2 is Low State and T1 is going OFF and C1 state is empty.

When we push the switch SW1 once, base T2 will pulled to Low to charging C1. This condition make T2 OFF for a second so collector T2 raise to High and trigger ON the state of T1. If T1 state is ON, collector T1 will pulled to Low and base T2 is latch to low although C1 is full or SW1 release. This condition make T2 state is latch to High. There is the toggle state logics of the circuit.

T2 and T3 is use to produce stable control voltage to drive transistor relay control. T3 also use to handle led D3, the display state of toggle switch. Relay RL5 is use to minimize switch wire to avoid interference that can make toggle circuit goes to error.

Relay Control

This circuit is use to control the state of the relay that control the solenoide valve. We must give two relay to control open relay and close relay .

This circuit is very simple. T6 to control the close relay and T9 to control the open relay. T5 is use to invert Low logic to trigger ON T6. Led D6 is use to display OPEN state of pneumatic and led D9 is use to display OPEN state of pneumatic.

The Limiter

This circuit is optional use to reduce noise from air flow in pneumatic. It also use to save life time the seal of the pneumatic. This circuit will turn off relay control when state is done.

This circuit is trigger by limit switch placed on the end of the pneumatic stroke. Limit switch is active low, so when stroke is done, base of transistor T8 or T11 has pulled to Low and flow current from emitor to colector. This current will drive T7 or T10 to turn off relay control.

This is the picture from diptrace PCB layout of the circuit above :

Top View

Bottom view

PCB file can be download from this link.