DESCRIPTION

This board is a variation of the PWM3B with an improved linearity, low output impedance and low ripple thanks to the use of a -12dB/Octave low pass active filter in the output stage.

Pulse width modulation to analogue converter board

Most small micro-controllers do not have real D/A converters to produce analog outputs, instead they provide PWM signals that can be converted to analog values using an LP filter. This approach is good enough to generate 0-3.3V or 0-5V analog outputs (depending on the logic level of the controller) to control small powered devices, but is not suitable to interface with high power systems, such as VFDs or Servo controllers for electric motors that typically have 0-10V analog inputs and recommend the use of galvanic isolation between the drive and the controller for improved safety.

This board provides the adequate isolation and level conversion to control the speed of up to three separate motors (or other devices) safely and precisely. The board requires a 24Vdc power supply and delivers and output level adjustable between 5V and 15V at full scale, making it directly compatible with most commercial drives. When using drives that only provide +10V auxiliar power it is possible to use the board by reducing the output level to 5v or 6V and adjusting the drive input to this range.

Each channel is totally independent and optically isolated from the other and the controller.

The board is fitted with standard 0.2″ terminal boards and can be housed in a commercial plastic enclosure with DIN rail mounting for easy addition to electrical control cabinets.

FEATURES

• Adjustable output level
• Optical isolation
• Independent channels
• Through hole components
• Socket mounted ICs
• Sturdy construction
• Fits in standard DIN rail enclosure (not upplied)

SPECIFICATIONS

• Number of channels : 3
• PWM input: TTL level. Max frequency 1KHz, 5mA @ 5V
• Output: Adjustable 0 to 5..15V
• Conversion system: MOSFET Totem-Pole
• Output filter: Low Pass 2 Pole Butterworth, 1.6Hz (-12dB/Octave)
• Output ripple: < 10mVpp at 500Hz
• Linearity: Better than 0.5% FSD
• Isolation: Min. 500 Vac
• Power: Nominal 24 Vdc (Acceptable range 10 to 30Vdc). At 10V the output level is limited to 5-6V.
• Dimensions: 3.400 x 2.700 in. (87 x 69 mm) 1.70 oz (0.055 Kg)

USAGE

Each channel is totally independent, therefore they can be connected to different controllers (if required). The same applies for the outputs.

ENCLOSURES

Can be purchased through distributors or online:

• Bud Industries - #DMB4772
• Digikey: DMB4772 - #377-1809-ND
• Mouser DMB4772 - #563-DMB-4772
• Newark DMB-4772 - #12T6241
• Velleman: GD4MG
• CamdenBox: CNMB/4/kit