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ord:electronics

ORD Bot Electronics Page

The ORD Bot is basically a RepRap type machine. There are several electronic options available.

RAMPS

This is the system I use. The RAMPS (RepRap, Arduino Mega, Pololu Shield) is a shield for the Arduino Mega. The current revision for this is the 1.4.

The controller is going to look like a three layer stack with the Arduino on the bottom, the RAMPS shield in the middle and the stepper drivers on the top.

You will typically need 4 stepper drivers X,Y,Z & E (Extruder). The Z is connected to both Z motors. There are two connectors on this axis. these drivers are usually Pololu A4988 drivers, but there is also the StepStick open source driver.

The RAMPS has (2) 12V inputs, one is 5A for the steppers and the other is 11A for the heaters. You can use a single 16A supply if you like.

The Arduino is powered by the USB cable connecting it to the computer.

You can buy it from

You can also see an example RAMPS setup.

ORDuino

Info coming soon.

See this post

Azteeg

This is a nice low cost solution with a built in arduino.

See the wiki page.

Sanguinololu

The Sanguinololu has the Arduino built in. It also uses stepper drivers from Pololu or the open source StepStick

MakerBot

MakerBot electronics should work, but I have not used them since my first machine.

Motor Drivers

The motor drivers are usually Allegro A4988 type driver chips. These are used on the Pololu and StepStick drivers. It is extremely important that you orient the drivers the right way and plug them into the right pins. They will explode…literally.

You need to set the current via a pot. You measure the voltage on a reference point while rotating the pot. If the control voltage is 5V, then the formula is V = I * .4. So for 1 amp you set the voltage to 0.4V.

Be careful not to touch anything near the reference point or you could explode the driver. I like to set the voltage with the motor voltage disconnected. The voltage is set from the 5V supply, so only the 5V needs to be on. Just hooking the Arduino to the USB should supply the voltage required.

The SureStep drivers from Panucatt will also run in the same sockets as the Pololu

Extruders

The hole pattern is design for direct mounting of the MakerGear Stepper Plastruder. The plate was design that simple flat adapter plates can be used to mount other extruders such as the MakerBot MK7 and the Wade's Extruder.

The MakerBot MK7 extruder comes with a thermocouple for temperature sensing. This is not compatible with the RAMPS as is. You will either need to purchase a thermistor to replace it, or a thermocouple amplifier such as an AD595 or a MAX6675, both of which are supported in Marlin firmware. It is worth noting that if you purchase a thermistor, use a common 100K type. Otherwise you will have to calibrate it in order to get accurate temperature measurements. Thermocouples need no calibration, but are more sensitive to electrical noise (such as generated by stepper motors).

Heated Beds

Heated beds are recommended for printing with ABS. I used a MakerBot Thing-o-matic heated bed for my Quantum and an eBay purchased MK2 for the Hadron. This is a cupcake heated bed as mounted on the quantum, detailing the wiring.
tinyworkshop.org_ul_ordbot_ord302.jpg
The wires from the build platform were run through a spring (McMaster-Carr PN 9664K17, 7” in length), and into the Z-Axis makerslide.

Limit Switches

The carriages have hole patterns for standard micro switch type limit switches. The t slots work great to locate the switch actuators. You can also use optical limits switches but you are on your own for mounting and make sure your electronics support that method.

Power Supply

The cheapest method of getting a good power supply is to use a PC power supply. The pin out of the main motherboard connector for a micro ATX power supply is below.

Color Signal Pin Pin Signal
Orange +3.3 V 1 13 +3.3 V & Sense Orange & Brown
Orange +3.3 V 2 14 −12 V Blue
Black Ground 3 15 Ground Black
Red +5 V 4 16 Power on Green (Short to ground for ON)
Black Ground 5 17 Ground Black
Red +5 V 6 18 Ground Black
Black Ground 7 19 Ground Black
Grey Power good 8 20 Reserved N/C
Purple +5 V standby 9 21 +5 V Red
Yellow +12 V 10 22 +5 V Red
Yellow +12 V 11 23 +5 V Red
Orange +3.3 V 12 24 Ground Black

!Picture removed !

Here is a simple modification I did to a 350 watt micro ATX power supply. I put two banana jacks on the side of the chassis as well as a switch to turn it on. The switch connects the wires that went to pins 16 (green) to 15 (black). I solder (2) yellow wires to the red jack and (2) black wires to the black jack. I used two to share the current.

Note: some power supplies require some amount of load on the other voltages, so you may need a power resistor on them.

Single Voltage Power Supply

This type of power supply is another good type to use. You probably want a 30A unit. You can usually find these on eBay for less than $30. They have a voltage adjustment pot that usually has about a +/-10% adjustment range. This can give you a little boost to overcome voltage drop in wiring and add give faster heating.

Power Cable.

There will be up to 20 Amps going from the power supply to the controller. At this current level you can have a voltage drop across the cable. If you get too much of a drop it could effect performance of the heaters and motors.

Voltage drop can be calculated with this formula.

E = R I
where
E = voltage drop (Volts)
R = electrical resistance (Ohms)
I = current (Amps) 

Typical resistance in wires are listed below.

18 Awg  0.013 Ohms/Meter
16 Awg  0.0085 Ohms/Meter
14 Awg  0.0067 Ohms/Meter
ord/electronics.txt · Last modified: 2013/08/21 10:59 by bdring