Ok thanks. PC1 should be accessible enough to solder.
And I guess Rodeastat would indeed be much more interesting for my application. But I've these couple Cheapstats already so I'll try to make them work before moving to the next generation.
Posts made by PJS
RE: Adding a relay for stirrer control
Adding a relay for stirrer control
I was wondering if it is possible to connect and control a relay on the ATXMega with a small modification of the electronic board? Is there an unoccupied output pin that could be used to send a small tension? The idea would be to add a stirrer to improve sensitivity.
I've made a few changes to the 111810 mcu program in order to implement an ASV procedure. If you are interested, it's here.
What was changed:
- ACV and CA methods removed.
- changed SWV to SWASV and SWCSV (with an changeable accumulation time + settle time of 2s).
- display of accumulation, settle and scan during the different steps of SWV (so it's possible to start and stop stirring during the different steps).
- Calculation of DAC in SWV changed from *(2048/1600)+2048 to *(4096/3300)+2048 to make it similar to CV, LSV and ConstVoltage (I am not sure why it was different in the first place, maybe someone can tell).
- different default settings for the methods. All methods use the 0-50µA default settings. I don't know why but it seems that the imposed potential with the 0-10µA range gets false very fast (false for E<-0.45V with 0-10µA and false for E<-0.75V with 0-50µA).
- modified the increments to change the settings of the methods (e.g. modification of the frequency in the SWV is made with a +-5Hz increment instead of +-1Hz).
- exchanged the edit and start position in the profile_opt menu. It avoids to start the methods inadvertently when selecting a method.
I have not tried all the methods. If something is not working, please let me know.
RE: LCD display problem
Ok, I realised this morning that I need both the flash and EEPROM files loaded on the apparatus. Yep, I'm a beginner in AVR
Also, I found that the initialisation of the different profiles on the EEPROM are in comment in the source file CheapStat_v2.c (from line 260). That's why no profiles appear in the main menu. So if you want to rebuild a flash and eeprom file, you need to remove the comments from this section.
When I'll finally understand all of this, I'll post my code. I'm trying to implement ASV.
LCD display problem
I have a problem using the files you provide for the mcu program.
If I upload the CheapStat_111810_EEPROM.hex file, it's working fine. However, if I try the same with the flash one CheapStat_111810.hex or if I build a new version, the display doesn't work properly (bad picture of it). During the first seconds, "Cheapstat" is displayed correctly however. This is only when the main menu should appear that it goes wrong. And when I randomly navigate, I sometime see the "edit / start" page.
Would you have an idea of what it is ?
Thanks in advance
RE: Cheapstat Lead determination
At this concentrations, it should not be too much of a problem to measure Pb, even though GC electrodes are not very sensitive. Is -400mV a low enough potential to accumulate Pb onto the electrode ? Have you tried at -0.8V?
Also, I don't know if there is Cu in your solution but I remember having some disappearance of the Pb signal with addition of Cu.
If it doesn't work, maybe try a gold electrode which is a bit more sensitive to Pb. Or maybe modify your GC electrode by depositing some bismuth on the surface.
RE: Cheapstat Lead determination
Which electrodes are you using, which parameters for your scan, what's the limit of detection you are trying to reach?
I am planning to eventually use the Cheapstat for field analysis of Zn, Pb, Cu and Cd but for now we develop the methods with a better potentiostat. I'll try to report here when I have some results.