Wednesday, October 20, 2010

Chapter 5 - Exercise 32 Update 5

Per Retrophile's suggested tip involving my relay being wired incorrectly, I changed the wiring and figured out my mistake (thanks Retrophile) - I assumed incorrectly that the relay's pins fit logically to the pin layout in the schematic... they don't. Going to the documentation for this particular relay verifies that Retrophile's pin layout is correct.

The two photos here show the rewired circuit - same circuit but just a slight change in photo angle for you to get a better look.

So, I've rewired the relay and as you can see in the first video below, the motor spins but the switches are still not causing the motor to stop and reverse. I used my multimeter to verify that I've got the switches wired correctly - the top and bottom pins are Normal Open (using the middle pin and bottom pin is Normal Closed and the multimeter shows a 1 when the button is NOT pressed... 0 when it is pressed). Per the schematic, we want the switches open, so I'm fairly sure I've got that wired correctly. I also replaced the 555 chip with a new one, just in case... but no luck.

So, my next step was to shoot another short video showing me using the logic probe on the 555 chip. My description here may not be 100% on the money, but as I understand the chip and the schematic, pushing a switch causes pin 2 to detect a drop in voltage... and causing pin 3 to allow current to flow (or is it just an increase in voltage - is voltage always present? Something to look into...)

As you can see from the video, putting the logic probe on pin 3 and pushing the power button causes the probe to change in pitch... that should be right. But then when I press any switch, pin 3 should change in voltage and be detected by the probe... but nothing happens. Any thoughts?

Friday, October 8, 2010

New web search tool

I will say that, up to now, I have much preferred to use versus - mainly because I've found Mouser to be information overload.

This morning I received an email from about a new web browser add-on for both IE and Firefox called the Mouser Search Accelerator... it'll basically allow you to highlight a component - a word, a part #, name, etc, - and then, without leaving the page you're on, perform a search of Pretty slick, and I think I'll give it a try soon. Let me know what you think if you give it a spin.

More information on it can be found here - it is something that must be downloaded and installed on your computer, btw.


Okay, I installed it on my Firefox (3.6) browser - as you can see, after highlighting an old part # from a previous post, I right click and select to search on - a little fly-out window appears with links to the part and a price... and look at that! The price hasn't changed since I ordered the part back in April 2010.

Thursday, October 7, 2010

Chapter 5 - Exercise 32 Debugging

Suggestions are coming in on ways to test or fix the problems I'm encountering. Let me explain what's happening now.

I've inserted the diode that j suggested... works! The buzzing has disappeared (see video below). So we're getting close. Right now, pushing either switch (that will serve the robot as a trigger to stop and back away from an obstacle) does not stop the motor from spinning - pushing either button is SUPPOSED to cause a drop in voltage on pin 2, so I think my next step is to use a chip tester to see if pin 2 is being triggered. (Right? No?)

I'm including some pictures here - one is the schematic and the rest are close-up photos of my circuit - maybe I've got an unseen error in my wiring. Be warned - my use of the breadboard is obviously that of a newbie, so I've got wires running all over the place. If I can't figure this out soon, I think I'll start over and try to rewire a bit cleaner and closer to the layout of the schematic.

Thanks in advance for all your comments and suggestions - I love learning by doing... and making mistakes is another favorite technique of mine as I tend to remember what I did wrong versus what I did right... and that's what drew me to this book in the first place!

First video below is WITHOUT the diode.

Second video is WITH the diode.

(FYI - family visiting this weekend so I may not get much more work done on this circuit until early next week.)

Chapter 5 - Exercise 32 Update 4

A short update today - only a small bit of progress... let me explain.

First off, I've gotten over sharing my dumb mistakes with the world via this blog... when you decide to walk through a book and perform all the tasks/exercises/experiments and share your results, you've gotta expect to have the occasional embarassing moment. I've had plenty during my tour of Make: Electronics, and I'm not done yet...

So, here's what happened - take a look at the schematic for Experiment 32 (if you have the book)... see that 50K trimmer there and how the left side of the resistor isn't connected anywhere? That's not an error... but I thought it was! So, I just connected that end where it felt right.

And... of course... the video yesterday shows my results. So, after Mr. Platt explained this little techy bit to me, I pulled that wire and ran the circuit. The motor still spins, but THIS TIME the two microswitches, when pressed, stop the motor. Progress. But not fixed.

Pressing either of the microswitches is supposed to reverse the motor's spinning for a short period of time. But it doesn't. Instead, pressing a microswitch causes the relay to buzz LOUDLY and the motor does stop rotating... almost. If you hold down the microswitch, the motor appears to stop but in reality it still rotates in the original direction but VERY slowly... almost impossible to see. Oh, and the relay buzzes LOUDLY! Release the microswitch and the motor begins rotating in the original direction again.

So, don't connect the 50k trimmer on both ends... just the one shown in the figure. And if anyone has any ideas WHY my relay is buzzing AND why either microswitch doesn't cause a reversal in the motor spin, please let me know... I'm taking a step back to think about this for a bit.

Wednesday, October 6, 2010

Components Pack 1 Frustrations

I just went over to the Components Pack 1 webpage to confirm the list of components in the kit... and I was surprised to find a large number of negative reviews... after reading over them, it appears that the kit has been out of stock for just over a month (earliest 1 star review was August 21... latest Oct 1).

I'm not sure what's happening, but if you're trying to gather up the parts on your own, I've tried to include my Shopping Lists in previous posts, including part#s and sources. I may have missed a few, but hopefully there's enough information there to help you consolidate some shipping from multiple sources. (Click on the Shopping List label to the right of the screen to filter the blog and display my shopping list articles... if I've missed one, please let me know.)

I know it's frustrating - I was already well into Chapter 4 when these kits became available and it would have been nice to have all these parts together in 2 kits. But hang in there - if you've got the book and are wanting to get into it, keep in mind that the Chapter 1 exercises are low-cost, really... I'm not counting the tools such as the breadboard, soldering iron, etc... I'm talking about the components like LEDs, batteries, a few capacitors, resistors... you can easily get deep into Chapter 1 before spending a lot of money and in that time, maybe Components Pack 1 will become available. (It looks like Pack 2 is still available.)

Chapter 5 - Exercise 32 Update 3

Before cutting out the wood for the shell of the robot, I figured it might be wise to actually wire up the schematic first and see if I can get all the electronics to work. As you can see from the video and picture, I've managed to wire up the motor - I've got a temporary push button that allows me to provide power to the circuit. I'll get an actual on-off switch once I get the circuit de-bugged.

The circuit is definitely providing power (6V) to the motor, but the two microswitches are not working as desired. When one is pressed, it's supposed to drop the voltage on pin 2, triggering the coil and reversing the spin on the motor... but that's not happening. Pressing either switch does not reverse the motor. I'm using different microswitches than the ones seen in the chapter, but I don't think that's the issue.

I also need to get out my chip tester and make sure that voltage is detected on pin 3 that runs to the coil.

Obviously, any suggestions my readers may have will be appreciated.