Tag: SPDT

Posted on by — 1 Comment

Velleman MK179

Completed Kit
Completed Kit

This is the Velleman MK179 Proximity Card Reader, which is supplied in kit form. In the image above you can see the completed kit, the read coil is etched onto the black PCB on the left. Bringing a recognised card close to the coil operates the relay on the main PCB for a programmable amount of time.

Main PCB
Main PCB

Closeup of the main PCB, 12v DC input at top right. Left IC is an LM358 dual Op-Amp, the IC on the right is a PIC12F629 with Velleman’s custom firmware.
Logic power is supplied to the ICs & the oscillator from the LM7805 regulator at the top of the PCB. The relay is a standard 15A SPDT 12v coil relay, with the switch contacts broken out onto the screw terminals on the left.

Schematic Diagram
Schematic Diagram

As it is not provided with the kit, unlike other Velleman kits, here is the schematic for this.

 

0
Posted on by — 4 Comments

Audi TT Roof Hydraulics

Pump
Pump

This is the hydraulic system from an Audi TT that would power the soft top. Here is the hydraulic pump unit. Oil Tank is on the left. Power is 12v DC at ~20A

Cylinders
Cylinders

The pair of hydraulic cylinders that attached to the roof mechanism.

Limit Switch
Limit Switch

One of the cylinders has a limit switch built in. The brass bolt coming out of the side of the head is one contact. The other contact is the cylinder body.

Hose
Hose

Marking on the hoses. This is Parker Polyflex hydraulic hose. 1/8″ ID.

Motor
Motor

Drive motor for the hydraulic pump. Standard DC permanent magnet motor.

Motor Suppression
Motor Suppression

Motor power terminals & suppression capacitors. As the reversing relays actually short the motor out when de-energized, there is a lot of arcing at the brushes without some suppression.

Reversing Relays
Reversing Relays

Reversing relay stack. Each relay is a SPDT configuration. The pair are arranged as a DPDT bank to reverse the motor, depending on which relay is energized.

Tank
Tank

Detail of the oil tank showing the level markings.

Power Valve
Power Valve

Solenoid valve on top of the unit. This valve provides full pump pressure to the cylinders when energized.

0