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Tuesday, 17 July 2012

LabVIEW: Simulating keyboard events

Another useful trick in LabVIEW using the user32.dll is to simulate keys being pressed on the keyboard. I haven't come across the need very often, however when using console applications, it can be necessary.

I ran into this problem while running a console application that runs a GPS simulator. Getting the application to run was easy and when the simulated trip is complete, the console closes automatically. The problem came in when I wanted to stop the controlling LabVIEW application. When I stopped the LabVIEW application and if the console was still running, I needed to close it and wanted to do it all in one step, instead of forcing the user to stop the LabVIEW application AND close the console window.

After some research I found out that the user32.dll has a keyboard event method so I decided to use that. I first had to make the console window active, find out how here, and then I would run this application as a sub-vi to simulate a Ctrl+C which was needed to stop the GPS simulation and close the console. 

What happens is that the two integers need to be passed to the dll. The first element is the decimal representation of the ASCII character that needs to be simulated and the second is what motion the button makes.

EG: 162 is represents the Ctrl key and 67 is the decimal representation for the ASCII uppercase C. The second integer that is passed to the dll is used to decide what the button is doing. 0 Simulates that the button is being pressed and 2 simulates that the button is being released.

Therefore, by writing each cluster to the dll in a for loop with 50ms delay between loops, Ctrl+C is written to the active console window which will stop the GPS simulation and close the window.

To download the example VI, use this link.


Friday, 13 July 2012

LabVIEW: Making a window active

A small issue that I have been trying to resolve is when a LabVIEW application runs and multiple windows are open, the need is often there to bring a window to the front as some stages of the application. 

Now I am sure there are many ways to perform this task, but the easiest and most reliable way that I found is to use the user32.dll that is part of the windows installation. This dll is easily accessed by using Call Library Function Node. This can be found in Connectivity >> Libraries & Executables.

The three methods that are used are FindWindowA, SetForegroundWindow and ShowWindow. By wiring these us and adding the correct window name that you want to bring forward, when the program is run whatever window name is selected will be brought to the front. 

There are many other tasks that can be performed by using the user32.dll. I have used it in a few other places in my programs and will add some more posts in the future of where it can be used.

To download the example VI, use this link.


Thursday, 12 July 2012

2W red LED bicycle light update

If you missed the first post about my modified bicycle light, take a look here

So I used my light last weeks at #moonlightmass and it was super cool. I got a few comments about how bright it is and I suppose it's not a great idea to use this light in a crowd of people. To be seen out on the road by cars, this light is great.

Here is a picture of the modified light mounted on the seat post with the battery pack and controller mounted in a box under the saddle.

Here is a quick video of the light in action.

There are still a few software changes that I need to do like complete the low battery indicator and I also want to add a few more light functions, but that will come when I get a chance.


Wednesday, 4 July 2012

#moonlightmass in Cape Town

What started in January 2012 as a social experiment over Twitter, has now become the place to be once a month when the moon is full. Meeting on every full moon under the round about in Green Point, the ride goes past the amazing Cape Town Stadium and onto Sea Point promenade. 

The ride then follows the promenade and past the Sea Point library up onto Main Road. Making its way back to the city center, the ride then turns up Long Street. For me this was the best part of the ride because how often do you see so many people riding their bikes up one of the busiest roads in town with zero cars.

At the top of Long Street the ride then crosses over and makes its way down Bree Street where it finishes at Greenmarket Square.

View #moonlightmass route in a larger map

So that is the route that the ride takes. It's a great concept and it was super to see the police out to help with the traffic control. Big up to the City of Cape Town for helping out. I can only imagine that next month is going to be even bigger so looking forward to that. 

Keep an eye on the #moonlightmass website for the next event, it's going to be large.


Tuesday, 3 July 2012

Bicycle light using two 1W red LED's

I bought a 1200 lumen light the other day so that I can cycle before and after work when it is still dark. It works really well to light my way, but I also wanted a decent back light. After all, the cars generally come from behind and need to see you.

Instead of simply buying one, I decided to make one by recycling an old bicycle light that I had lying around and use two 1W red LED's that I have also had for a while and never used.

The first hurdle I had to overcome was to design a power supply capable of delivering at least 350mA and one that could supply 6.4V, enough for two LED's. I also wanted to use at the most, two 1.2V NiMH batteries.

The next choice I had to make was what controller I wanted to use. I settled on a small, low cost micro controller. I also decided to run the entire circuit off 5V. This would slightly under drive the LED's, but would safely power the micro without using two power supplies.

For the power supply, I went with the LM2623 which is capable of supplying 2A with an input of as low as 0.8V.

For the micro controller I went with the PIC12F615 which has an internal nMCLR pull up and an internal 4MHz oscillator which keeps the pin count low.

To drive the 1W LED's, I am using a BD139 transistor. I am driving it just below its limit, but I had a few lying around so just used one. I am using a PWM signal of 1KHz and the LED's are on for 50ms and then off for 250ms. At the moment I only have one setting but I plan to add more in my next version, different flash rates and solid on.

I use one of the analog inputs to measure the battery voltage. By doing this I can turn on the 3mm LED when the battery voltage goes below 2V. This means that I won't run the battery's too flat and damage them.

The battery's and controller are housed in a plastic box which I have tied neatly under my saddle and the light is attached to my seat post. 

At the moment this is my prototype which works, but isn't 100% complete. I still need to tweak the part of the program that measures the battery voltage and I also want to play around with the current limiting resistor so that I can get the max brightness out of the 1W LED's. I also have to test how long the circuit will run on two AA battery's.

I will be testing it tonight at Cape Town's #moonlightmass to see how it performs. I will also get some pictures or videos and put them in a follow-up post. 

If you want the DesignSpark schematic and the micro controller code, use this link.