T-baneklokke - coundown clock

Some time ago I grew tired of my wife asking if she had to leave soon to get to the metro in time. I did what any sensible techie would and made her a battery powered countdown clock.

The clock counts down to a selectable time, and repeats the countdown every 15 minutes (the normal interval for the metro over here). Three minutes before it is time to leave, the clock display starts flashing slowly to get your attention. Then, once you should have left, the clock counts UP, blinking fast, as you still have time to make it if you walk briskly. Once your time is TRULY up the countdown to the next metro starts.

To save batteries, the clock goes into as low power mode as possible after about an hour, and you have to switch it off and on again to restart it.

The clock is built using an Arduino, and has a battery powered real time clock to remember the time while powered off.

To make it truly stand alone I added the possibility to set the time and time-to-leave using buttons.

The clock was built into a custom made plexiglass box, and the outside covered with a design printed onto photo paper with a sticky back side. I used my wife's Cameo vinyl cutter printer to cut the paper - I just love that machine!

Here are some pictures from the process:

The Arduino with the RTC module to the right, time-set buttons in the middle and 7 segment display at the bottom.

To keep the top and bottom of the case in place while gluing on the sides, I built a little Lego rig. We all use Legos for prototyping, don't we?

The finished box

Sanded down to make the photo paper stick. 

Power switch and stand-offs added.

Everything fits snuggly. Notice that I kept the USB input to be able to update the software if necessary

Voila! The finished product. Now my wife is never late for the metro ever again. Riiight.

Roland resistor nets for the IR3109

While researching IR3109 based filters I came across the schematics for the Jupiter 6. It has a neat multi mode filter, but the schematics show three resistor networks, and the resistor values for those are not shown.

Luckily, someone has figured out that the same resistors are used in the MKS80, which has most of the values - though not all of them.

From a bit of guessing I have come up with what I believe is the values and internal connections.

RM0688 - The schematics do not show the value for the resistor between 2 and 3, but it is rather safe to assume that it is a 100k resistor like all the others.

RM0690 - The MKS80 schematics shows a 7.7k resistor between 2 and 1. The Jupiter 6 schematics show two resistors without values, one from 1 to 2 and one from 1 to 3. As a 33k and a 10k resistor in parallel equals a 7.7k resistor, and these values are already used in the net, it is very likely that these are the missing values. If we at the same time assume that the positions are reverse those in the other half of the net, just like in the RM0688, we get the schematics above. PS: I have yet to see a usage of this net where 2 and 3 are not connected, so it is in reality only the combined value that matters.

RM0891

The resistor nets have different part numbers and designations in the various synths:

13919128 - RM0688 - RKM8C066
13919130 - RM0690 - RKM8C068
13919132 - RM0891 - RKM9F561/683GP