Capolight electronics projects. a collection of reprap, led and rc projects gas variables pogil worksheet answer key


In series with the input to the heated bed was placed the bi-metal switch so that in the even that it becomes stuck on full power it should still stay within a safe temperature range. Note that you can use a bi-metal switch as a method of temperature control on its own but that they tend to become stuck after a few thousand cycles. The MOSFET board was connected directly to the power-supply and switched with the relay output of the temperature controller. Note that the MOSFET board requires 12V to turn on and so I used a simple voltage divider to drop the 24V down to 12V.

The temperature controller can be powered off mains AC or 24V DC. I decided to separate the high voltage mains from the low voltage components via a dividing wall and power the temperature controller off 24V. This design is made so that the whole Cetus 3D printer can safely sit on top of the enclosure which keeps the foot print nice and small.

Note that I initially printed the red lid first using the default Cetus print settings (and then ran out of filament) and the final result was pretty bad. After looking around on the cetus forums it looks like there is a problem with the included slicer when printing without a raft. specjalizacja z gastroenterologii To solve this I switched over to the excellent Simplify 3D slicer. After a few hours of adjusting the settings I managed to get great results. If your interested you can find a copy of my final settings here.

The pitch diameter of a belt is the diameter of the belt as measured at the reinforcing steel wire. To estimate the pitch diameter of this belt you just calculate the circumference (50 teeth * 5 mm pitch = 250 mm) and divide by pi (250mm / pi = 79.58 mm). When we turn the belt inside out (invert it) this length should remain the same due to the steel wire. The rest of the belt however will become compressed/stretched to accommodate the new shape. Thanks to this this handy timing pulley diameter calculator created by droftarts on his parametric pulley page we can see that the pitch line offset for a HTD 5M belt is 0.5715 mm. That is the distance from the pitch diameter to the base of the tooth. This distance will be the same when the belt is inverted and so we now know the distance to the base of the tooth will be:

One assumption that I made with this belt is that the majority of the flex occurs in the valleys rather than the teeth and so I have modelled the belt accordingly. This involved generating 3.05 mm teeth diameter spaced 7.2 degrees apart with the valley distance increased to make up the gap. For comparison the image below is of a the same belt but not inverted. Notice that the valleys are slightly different in size.

With the inverse belt design its time to move onto the circular spline. electricity physics The construction of the circular spline is exactly the same as the inverse belt discussed above with the exception that the grooves are concave and facing inwards. For the circular spline I have selected 54 grooves for a gear ration of 12.5:1 (50 / (54 – 50) = 12.5 : 1).

To determine the correct shape of the wave generator and thus the scaling of our flex spline in two dimensions we can consult this ellipse calculator. I used the base of the teeth for reference of the starting circle and the matching base in the outer ring for the widest diameter after deforming. The spreadsheet just estimates the minor axis of an ellipse that maintains the same area as the starting circle and displays the required scaling for the flexible spline. Once applied to the flexible spline it now meshes with the circular spline.

Moving on to the flex spline cup. This component will need to be attached to the flex spline belt by some means, possibly a flexible glue. The flex spline cup acts to hold the flex spline belt in place and stop it from rotating and thereby allowing it to do usable work to the circular spline. gas and sand This cup was generated by creating a circle a desired distance below the deformed flex spline belt and then using the loft feature to generate the geometry. Note that you will need to loft a solid body first then create an offset top and bottom to loft cut out the middle.

The belt has a 5mm pitch (peak to peak), a tooth height of 2.08 mm, a total belt thickness of 3.81 mm, a the tooth width is 3.05 mm, a radius of 1.49 mm and a valley radius of 0.43 mm. Note that the image below is one of many you will find online that shows an incorrect tooth profile! If you use the dimensions shown below to make the pulley in CAD it looks like that shown by SDP-SI with a flat valley.

• Zooming back out we now need to sketch the tooth pitch. For our 50 groove pulley we will have a tooth every 7.2 degrees (360 degrees / 50 grooves = 7.2 degrees). Sketch a construction line 7.2 degrees away from your first circle with the origin as your point of rotation. In the example below the angle is measured from the horizontal and so becomes 90 – 7.2 = 82.8 degrees.

• In this second last step we use the centre point arc tool to sketch the inner circles of the pulley profile and finish it off with a single straight line segment be tween the two 0.86 mm dia circles. Note that in order to get the lines to meet exactly you may need to turn off grid snapping using the icon on the bottom of the window. With this done our pulley profile is now complete.

Simply tell a stepper motor how many steps to move and in what direction. Easy. Depending on the control electronics, a servo motors may also be used in a simple step/direction setup. electricity facts However, to really make use of its performance careful tuning of its PID parameters under both static and dynamic conditions is needed. Granted, good control firmware can just about take care of this for you these days but it is still definitely something to consider if you are changing the loading which the motors are placed under on a regular basis (ie: different sized parts on an an XY table moving at high speeds) or if you ever decided to roll your own electronics and firmware.

When I say ‘dedicated servo motor’ I mean a servo motor that is designed from the ground up to be a servo motor, and not a modified stepper motor. The key difference being that a dedicated servo motor will generally nothave pole plates with teeth (with each tooth acting like its own pole pair) and will generally have a lower winding inductance than a stepper motor of equal size.

If you need a powerful motor in a small, lightweight frame that you can also precisely control then a servo motor is really your only option. For example, servo motors are almost exclusively used to drive industrial robotic arms as the amount of power ( torque x angular speed = power) you can produce for a given motor size is considerably larger than an equivalent stepper motor.

Lets compare a Nema23 stepper motor from Pololu with a Hudson-series M-2310 Clearpath servo motor. Both motors have roughly the same frame size and yet the stepper is nearly twice the weight of the servo at 1.05 kg vs 0.63 kg while producing around 30 % less holding torque at 1.9 and 2.7 Nm respectively. However the real difference comes from the peak power produced by each type of motor. By using the torque torque curves from the stepper motor data sheet and assuming a simple linear reduction in torque for the servo motor to around 6000 RPM, 2000 RPM higher than its listed maximum speed of 4000 RPM (I could not find a torque curve for Clearpath motors) we can compare the peak power produced by each motor.

This difference in output power is due to the high number of poles (200 for 1.8 degree per step) found in a stepper motor that are needed o achieve its fine position control. This high number of pole pairs comes at the expense of maximum rotational speed and torque, greatly limiting the available power the motor can produce. Servo motors on the other hand are fundamentally no different to a BLDC motor. The next step: Converting cheap and extremely powerful ‘hobby’ BLDC motors into servo motors with Odrive

Each ODrive controller board is capable of controlling two motors which are often smaller and lighter than a nema23 stepper motor but can be capable of producing many time the power and torque of even a clearpath servo motors. This is possible because these motors have been designed to be as powerful as possible at the expense of durability and efficiency. So while these motors are not suitable for industrial environments they could be of real interest to the DIY community.

The Odrive controller also has some interesting features such as the ability for regenerative-breaking. This is incredibly useful even outside of transportation applications as it makes it easy to safely remove unwanted power from your system during rapid deceleration without running it backwards through your power-supply, potentially damaging it. The Odrive is also designed to be powered in tandem with a hobby-grade Lithium polymer battery. This is also very important in order to achieve the full capabilities of these BLDC motors, which can have peak power draws in the multi-kW range. electricity distribution network By using a high discharge Lipoly batter as a temporary energy store it becomes possible to draw the full 2 kW needed during rapid accelerations while still powering the whole system off a modest power supply.