Propeller Clock on a Mirror.


Frequently Asked Questions

Warning !!! This webpage was never intended to be a complete step-by-step building guide so that just anybody can make a propeller clock. There are several web-pages describing such a clock. This one is just my note how I did it.

If you like to build our own clock you will need a fair knowledge of electronics, micro-controllers, mechanics. Some basic knowledge in physicsí, aerodynamics, fluid mechanics, quantum theory,.. might come in handy


Q: Can I buy a kit with all components ?
A: Not from me! I have no commercial interest in the project. I donít sell kits.

Q: Can I buy a complete clock ?
A: same answer as for kits.

Q: Where can I buy the components ?
A: Depends on your location. I donít know where you can buy components. There are no critical parts in the clock. If you canít find the exact same component then there is sure to be a suitable replacement near you. This is where you will need knowledge about electronics.

Q: Location of the IR led and IR sensor ?
A: It is not important how and where you mount these. Just make sure the ir-sensor is illuminated once every revolution. Even the position of the rotor where this happens is not critical, you can adjust this in the software. In my design the ir-sensor is active when the rotor is at the 11 oíclock position. If this is different for your hardware then you need to modify the prop.asm file. Find the sub-routine InitRam and locate the following lines. Here is where your knowledge in micro-controllers comes in handy.

movlw 0x37 ; Initial Display Offset for my hardware !!!
                movwf DispOffset ;

Q: Where can I buy the MIC2941A or a replacement ?
A: Replacement for the MIC2941 would be the LM2941, but is equally difficult to find. It is a low-drop linear adjustable regulator with an ON/OFF function. The 2941 is used to adjust the speed of the motor and to allow the PIC to turn the motor on and off. A good alternative is the more common LM317 as regulator (without ON/OFF). Then add a MOSFET or even a relay to switch to motor ON/OFF.

Q: Where can I buy Nichia LED?
A: From Nichia,Ö if you buy them by the thousand. Otherwise you can try to find bright leds from of You need a led with a high light-output. Below 200 mcd will give a poor result.

Q: I donít understand the general concept of the clock
A: re-read the content of the web-site until you do understand

Q: I would like to build this clock but need more documentation (diagrams, s/w flowcharts,Ö)
A: All documentation I have is already on my website. If canít find it, I donít have it. Donít mail me for extra documentation !!!

Q: I donít understand the concept of the rotating transformer.
A: This rotating transformer is needed to feed electricity to the propeller electronics. It more or less works as a normal transformer where you put energy in the primary and get energy out of the secondary coil. Except, the pri. and sec. are not mechanically attached to each other and therefore the sec. coil can turn around. The magnetic coupling between the coils is by air-gap which results in a transformer with very poor efficiency.

Q: My rotating transformer isnít working properly.
A : It is very difficult to make a good transformer. The airgap between the two coils must be as small as possible. If you donít success in make a good transformer, your best option is to use slipring contact to feed the propeller. Check out  Luberth Dijkman's web-site to find out how he did it.

Q: What is TP1 on the propeller schematic?
A: a test point. Here you should measure a 2.5kHz square wave. Use an accurate frequenty counter to adjust the 20Mc X-tal oscillator.

Q: What remote control did you use ? Did you make your own?
A: No, I did not make my own remote control. I used an existing remote control from a Barco large screen projector. This is a remote control that uses the Philips infrared protocol known as RC5. Any remote control working with RC5 can be used for this project. Some modifications for the file keys.asm may be necessary.

Q: I have a remote control, how do I know if it transmits RC5?
Q: How do I know the address the remote is using?
A: Capture the output from the IR-receiver on a DSO (digital storage scoop). Check if the captured pulse comply with RC5 standard. Then manually decode the pulses to calculate the address. Here you find good explanation about infrared remotes and the RC5 protocol.

Q: How do I program the PIC ?
A: I used the PicStart Plus programmer from Microchip. You can also build your own programmer. There are hundreds of site with information about simple and cheap programmers. Do a web-search.

Q: Is there a PCB design available ?
A: Not from me, I only made the clock on a prototype board. But others have made PCB's. Sven allowed me to post his protel files. You can donwload a trial version of protel from And here are the protel files from Sven (Self-Extractor)