Lee Solenoid Valve Drive Circuit Schematics

The coil inductance and the resistance affect the valve's response time by opposing changes in the coil current. The time constant shown in the Lee Solenoid Coil Electrical Characteristics table is the time required for the current in a valve coil to reach 63% of its steady state value, when subjected to a step voltage input. When the solenoid valve is turned off, the energy stored in the coil's magnetic field will be dissipated by some means, usually through a diode to keep the circuit operation within predictable, safe limits. Several proven circuit designs to optimize response time or power consumption are presented on the following pages. These designs are 'typical' circuits and components listed are typical for Lee solenoid valves. For additional circuits (for specific valves or pumps), contact The Lee Company for assistance.

Basic Transistor Driver Schematic

(Lee Drawing LFIX1001850A)

All Lee solenoid valves can be operated with a variety of circuits, the simplest being a transistor and diode with varying additional complexity depending upon the performance demands of the application.

Note: Vcc = Required Lee Co Solenoid Valve Operating Voltage

Spike and Hold Driver Schematic

(Lee Drawing LFIX1001750A)

This circuit can be used as either an enhanced response time driver or as a low power consumption driver. As an enhanced response time driver, select V1 (usually 2-4 times the rated voltage of the valve being driven) as required to obtain the desired valve response. V2 is the nominal rated valve voltage. Choose values for R1 and C1 to determine V1 pulse duration.

As a low power consumption driver, V1 is the rated valve voltage and V2 is one half the value of V1. This serves to provide full actuation voltage to the valve, which reduces the applied voltage by 50%, thus reducing the valve's power consumption by 75%.

Notes:

  1. Do not exceed the valve's maximum power rating.
  2. V1 Pulse Duration = 1.1 x R1 x C1. Adjust values as required to obtain desired pulse duration.
    For C1 = 0.047 µF, R1 = 100k pot, spike time range is 0.05 – 5.0 ms.
  3. Vcc range recommended = 4.5 V to 16 V
  4. V1 = Required valve spike voltage. V2 = Required valve nominal hold voltage.

Fast Response Driver Schematic

(Lee Drawing LFIX1001800A)

The response time of most Lee solenoid valves can be reduced by operating the valve at a higher than normal supply voltage in conjunction with a properly selected zener diode. When used in this manner, care must be taken that the power rating of the valve is not exceeded. Excessive heat may cause damage. Calculate the power (P = V2/R) and multiply this by the percent on time in the duty cycle. The result is the mean power dissipation, which should be less than the valve's maximum power rating.

Shown below is a typical circuit designed to enhance the response time of a Lee solenoid valve.

Note: Vcc = Required Lee Co Solenoid Valve Operating Voltage

Low Power Consumption Driver Schematic

(Lee Drawing LFIX1000650A)

This circuit provides a 70% reduction in valve power consumption. The valve is actuated with the full design voltage and then held at a holding voltage of approximately one half of the design voltage. The additional voltage required to actuate the valve is stored in the capacitor C2. When the control voltage signals the valve on, the transistors are switched such that C2 doubles the supply voltage and discharges through the valve coil. Recommended values for various valves are given in the table on the following page. Resistor R3 determines the peak current and rate of recharge and should be sized according to the particular application.

Notes:

  1. Do not exceed the valve's maximum power rating.
  2. V1 Pulse Duration = 1.1 x R3 x C2. Adjust values as required to obtain desired pulse duration, spike time range varies between 2.6 – 26 ms depending on valve design and R3 value chosen.
  3. Vcc range recommended = 4.5 V to 16 V
  4. V1 = Required valve input voltage. V2 = Required valve hold voltage.

Low Power Drive Circuit Resistor (R3) Selection

Swipe to the right for more table information

VALVE
TYPE
V1 ACTUATION
VOLTAGE
(COIL DESIGN)
COIL
DESIGN
POWER
(mW)
V2 HOLD
VOLTAGE
HOLD
POWER
(mW)
C2
CAPACITOR
(µF)
R3
RESISTOR
(KΩ)
LHD 5 550 3 198 0.047 56
12 550 6 137 0.047 51
24 550 12 138 0.047 62
5 750 3 273 0.047 75
12 750 6 187 0.047 56
24 750 12 188 0.047 56
LFA 5 280 3 105 0.047 120
12 280 6 72 0.047 330
24 280 12 69 0.047 100
5 490 3 176 0.047 91
12 490 6 217 0.047 120
24 490 12 122 0.047 120
5 780 3 281 0.047 91
12 780 6 195 0.047 510
24 780 12 195 0.047 110

Latching Valve Driver Schematic (H-Bridge Design)

The Lee Company's LHL Series latching valves are designed to operate on 10 ms (min), bi-directional pulses. When integrating these latching valves into a system, only a single driving supply is needed. An H-Bridge circuit can be used to switch current direction (an additional logic supply may also be needed depending on the individual application). Most H-Bridge drivers such as Freescale's 17529 or 33886 would be suitable for the task, depending on how many valves are to be driven, the valve's specified voltage, PCB space constraints, etc. Regardless of the H-Bridge used, the following tips should lead to success when designing an electrical circuit to drive such a valve.

  1. Connect the logic supply and driving supply. These are normally separate power supplies (one to drive the logic circuitry in the application, such as microprocessors, and another to drive the valves themselves), though they can be the same
    supply under certain circumstances.
  2. Connect any enable/disable inputs of the H-Bridge to the appropriate logic. If the H-Bridge is to remain on, connect the enable/disable input(s) to HIGH or LOW (depending on which level asserts the input).
  3. Ensure that any charge pump capacitors are attached. Refer to the H-Bridge manufacturer's data sheet and use the recommended values.
  4. Design adequate power supply decoupling. This can often be achieved by connecting capacitors across the supply terminals. The H-Bridge manufacturer's data sheet may have device-specific tips.
  5. Design the logic which will control the H-Bridge. This can be done easily with a microprocessor or with combinational logic. The basic logic is described below:
    1. To switch the valve for Common to Port-A flow...
      1. Enable the H-Bridge if it is not already enabled. Refer to the H-Bridge's data sheet to determine whether or not the disable-enable delay is short enough to enable/disable on the fly.
      2. Drive the H-Bridge in its forward operation mode. The exact logic to do this will be in the H-Bridge manufacturer's data sheet, though it typically involves setting one input HIGH and another LOW. This will apply current in the forward direction through the valve.
      3. Wait 10 ms (min). This will allow the valve to shuttle and become magnetically latched.
      4. Stop current to the valve. This can be done by either disabling the H-Bridge (in which case the enable-disable delay of the device should be investigated) or by setting both H-Bridge inputs to either HIGH or LOW.
    2. To switch the valve for Common to Port-B flow...
      1. Enable the H-Bridge if it is not already enabled. Refer to the H-Bridge's data sheet to determine whether or not the disable-enable delay is short enough to enable/disable on the fly.
      2. Drive the H-Bridge in its reverse operation mode. The exact logic to do this will be in the H-Bridge manufacturer's data sheet, though it typically involves setting one input HIGH and another LOW. This will apply current in the reverse direction through the valve.
      3. Wait 10 ms (min). This will overcome the magnetic latching force and allow the valve to shuttle in the other direction.
      4. Stop current to the valve. This can be done by either disabling the H-Bridge (in which case the enable-disable delay of the device should be investigated) or by setting both H-Bridge inputs to either HIGH or LOW.

An example utilizing Freescale's 17529 as an H-Bridge drive with two LHLA0521111H valves is shown below. This sample implements two, 5 volt valves, cycling at 10 Hz. The valves are cycled at different times to reduce peak power supply current. Refer to the waveform in the graph below.

Dual, 5vdc, Latching Valve Driver Schematic

(Lee Drawing LFIX1001900A)

Waveform Graph

Quad, 5vdc, Latching Valve Driver Schematic

(Lee Drawing LFIX1001950A)

 

<< Engineering Data