Hi I'm new here and very lost when it comes to circuits. Im in my 4th year of mechanical engineering at uni, but from our circuits classes I've never taken away anything practical. I understand quite a bit of theory and can use a breadboard, but when it comes to designing something practical and implementing it I have no clue where to start. So I'm looking for help please!

My group for a machine design project doesnt really have a clue about how to design our circuit - so Im trying to learn. We're making an automatic snowboard waxing machine that essentially heats up the wax, dispenses it over the base of the board, and follows with a scraper that presses the liquid wax into the cracks and scrapes off excess. For heating, we have four hot plates taken from two hair straighteners. Both have a little circuit with them that has an on-off switch and a temperature control dial and a little LED for when its on, the circuit connects the two hot plates. The group wants the waxer to move across the board using a motor (the waxer is suspended over the board on tracks - gears meshed with a timing belt basically).

One group member said: 'If you want to write out the circuitry: There's one motor, and 2 straightening irons (I have a second one for the other side). The straightening irons should use the 4 heating pads with a control unit out of one of the straighteners and we also need to find a switch for the motor. Both the motor and heating portion should be in independent of one another, meaning that you should be able to turn on only the motor or only the heating unit.'

Then he tasked me and another girl with trying to make the circuit by wednesday which is when our next progress report is due... but neither of us have any idea how to start! We have access to a circuits lab, circuit software, and can play around with a breadboard.

Can anyone help us with this?

 

If you can come up with a working design by Wednesday, there may be a position open for you!!

If this is a practical design task, The first thing to do usually is to draw out the automatic process in a flow chart form.
How much is automated?, what operator input is required? IOW Manual, Automatic, or semi-automatic etc.
You also have to know the the power requirements for each part of the machine and how you intend controlling them in order to create a wiring diagram.
Then there are the mechanical constraints of torque etc required to move the various elements of the machine.
Not a trivial task for a two or three day project.
Max.

 

Haha well okay sorry let me clarify, we want to have as much as we reasonably can by wednesday for the progress report, cause the progress report is worth 10% and we don't want to go saying we haven't figured out the circuit yet (I know I know, procrastinators, but lets put that fault behind us and try to figure this out!). The motor itself has the following specs:

• Speed 118 RPM
• Voltage 115 AC
• Amperage 1.48 Amps
• Rotation CW
• Duty Intermittent
• Enclosure Open
• Mount 4 bolt face 1-5/8" x 1-9/16"
• Shaft 1/4" diam. x 15/16" w/ 3/32" diam. x 1-1/8" cross pin
• Size 3-1/4" x 2-3/4" x 4"
• Shpg. 4 lbs.

Now, I'm also pretty dumb when it comes to motors (you may wonder at what Ive learnt in the past four years), but the guys in the group are very confident that they know what they're doing and that this motor is exactly what we need. Despite their hesitance to sit down and talk the rest of us through how it'll work, Im trying to trust them. Personally, I'm comforted that there is the back up plan that if the motor doesn't get sorted out we can always resort to using a hand crank.

How much is automated? Either all the operator has to do is put in the wax, turn on the heating, then after a few minutes turn on the motor to get it going, or they have to turn on the heating then move the dispenser across the board by hand once the wax is heated.

Heres two pictures of the hair straightener plates with their little circuit board - looks like it has 5 resistors (from top-bottom, left-right they read 154, 1001, 683, 105, and 1000 respectively), 5 diodes (I can read two of them saying M7 and S2M - not sure what that means though), a capacitor (22 mircoF, 10V), an LED, and then whatever Q1 is. Also the switch says 1A, 125V AC on it and the dial is that middle silver piece with the black circle.

Here's what I think we need:
- wire the two sets of hair straightener parts together so they heat up together at the flick of one switch
- connect the motor such that it uses the same power supply but a separate switch
- to not hurt ourselves in the process

Soooo... I know this is a big project and it's not going to be done by wednesday, but maybe if we can at least understand what components we can use to make it work? Like do we just cut the wires from the other two plates and connect them into this circuit in the picture? In parallel with the two plates already attached?

Thanks for your quick reply btw!

 

As far as controlling the four heating pads. Each two pads have On/Off switch. Heating Pads 1 have On/Off Switch 1. Heating Pads 2 have On/Off Switch 2. Each switch has two terminals, this is where wires attach to the switch, call them Positive Terminal and Negative Terminal.

Attach a wire from Positive Terminal of On/Off Switch 1 to Positive Terminal of On/Off Switch 2. Attach a wire from Negative Terminal of On/Off Switch 1 to Negative Terminal of On/Off Switch 2. Now you have the two switches in parallel. When you close one switch, the circuit is complet and all four pads are powered up.

I had multidisciplinary project for my Senior Design. It was prototype for an industrial cooling system that used liquid coolant. We had 3 mechanical engineering students and 2 electrical engineering students (me being one of the electrical). I am very surprised that you got only mechanical students in your project.