Hardware
Will describe requirements
The Motor Driver used on the new version of AstroEQ is the DRV8825 Stepper Driver which is capable of providing up to **1.5A **without a heatsink.
The driver current limit can be set to suit your motor. The limit is set by adjusting a potentiometer on the motor driver boards. The potentiometers look like a cross cut screw head. Turning them Clockwise INCREASES the current and vice versa. The current can be measured by using a voltmeter to measure the voltage at the reference test point. This voltage can be converted to current as: Ilimit = 2 x Vref
The power input has a protection diode designed to run at >4A continuously, meaning that it shouldn't heat up and thus doesn't need a heatsink. By using this diode, the board is protected from accidentally connecting a supply with the wrong polarity. Care should be taken when installing the diode to make sure it is the correct way round.
The board should be supplied with no more than 15V DC, and no less than 9V DC. For best performance, a 12V DC Supply capable of sourcing a current of 4 times the limit current.
There is an onboard LM78L05 Regulator to supply the Atmega IC with a regulated +5v supply. As such, if the power is disconnected, the whole board, except for the USB-Serial port will be shut down. This means that you can reset the board by simply unplugging the power.
By using an onboard regulator, AstroEQ is compatible with USB hubs which can only supply a small amount of power. The AstroEQ5 board draws <30mA from the USB hub meaning it is fully compatible with bus powered usb hubs.
At the moment, AstroEQ is only capable of driving Stepper Motors, so is not compatible with mounts which use either Servo or DC Motors. Furthermore, only 2 phase Bipoloar stepper motors are supported, however Unipolar motors can be used by leaving the centre tap unconnected, and 4 phase motors can be connected by wiring pairs of phases in series.
###For the Through Hole Version
####Resistors:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 5 | 1kOhm | 9342400 | MULTICOMP - MF12 1K - RESISTOR, 1K, 0.125W, 1% |
| 2 | 10kOhm | 9342419 | MULTICOMP - MF12 10K - RESISTOR, 10K, 0.125W, 1% |
####Capacitors:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 7 | 100nF | 1100367 | AVX - SR205C104KAR - CAPACITOR, 0.1UF, 50V |
| 3 | 100uF | 9451188 | MULTICOMP - MCGPR25V107M6.3X11 - CAP, ALU ELECT, 100UF, 25V, CAN |
| 1 | 470nF | 1457660 | KEMET - C320C474M5U5TA - CAPACITOR, 470NF, 50V, Z5U, 2.5MMP |
| 4 | 22pF | 1100369 | AVX - SR151A220JAR - CAP, CERAMIC, 22PF, 100V, C0G/NP0 |
####Crystals:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 1 | 16MHz | 1842217 | TXC - 9B-16.000MEEJ-B - XTAL, 16.000MHZ, 18PF, HC-49S |
| 1 | 12MHz | 1842203 | TXC - 9B-12.000MAAJ-B - XTAL, 12.000MHZ, 18PF, HC-49S |
####Connectors:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 1 | USB Connector | 1125347 | MOLEX - 565790519 - MINI USB TYPE AB, RECEPTACLE, THT |
| 1 | Program Header | 3418492 | TE CONNECTIVITY / AMP - 826632-3 - HEADER, 2ROW, 6WAY |
| 1 | Power Jack | 1737246 | MULTICOMP - MJ-179PH - SOCKET, LOW VOLTAGE, 12V, 5A |
| 2 | RJ11 Connector | 1560166 | MOLEX - 95501-2641 - JACK, 6/4 LOW PROFILE |
####Case:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 1 | HAMMOND-1593N | 9287566 | HAMMOND - 1593NBK - CASE, ABS, HANDHELD, 110X75X25MM |
####Semiconductors:
| Qty. | Value | Farnell Code | Description |
|---|---|---|---|
| 1 | ATMEGA162-16PU | 9171169 | ATMEL - ATMEGA162-16PU - IC, 8BIT 16K FLASH MCU, DIP40, 162 |
| 1 | PIC18F14K50-I/P | 1648501 | MICROCHIP - PIC18F14K50-I/P - 8BIT MCU, 16K FLASH, 768 RAM, PDIP20 |
| 1 | 78L05 | 1467367 | FAIRCHILD SEMICONDUCTOR - LM78L05ACZX - IC, V REG, 5V |
| 3 | Red LED | 1142499 | KINGBRIGHT - L-424HDT - LED, FLAT TOP, 3MM, RED |
| 1 | C3D06065A | 1864928 | CREE - C3D06065A - DIODE, SCHOTTKY, 6A, 650V, TO-220 |
| 1 | 1N4148 | 9565124 | MULTICOMP - 1N4148. - DIODE, 100V,150MA, DO-35 |
####Driver Boards:
| Qty. | Value | Pololu Part No. | Description |
|---|---|---|---|
| 2 | Driver | #2133 | Pololu DRV8825 Motor Driver board |