Differences
This shows you the differences between two versions of the page.
| Next revision | Previous revision | ||
| michka:research:microbial_fuel_cells:cardiff5 [2016-09-19 08:47] – created michka | michka:research:microbial_fuel_cells:cardiff5 [2016-09-21 09:56] (current) – michka | ||
|---|---|---|---|
| Line 1: | Line 1: | ||
| =====MFCitizen @Cardiff===== | =====MFCitizen @Cardiff===== | ||
| - | ===September 7th-9th, 2016=== | + | |
| + | **[[http:// | ||
| + | |||
| + | {{: | ||
| ====Abstract==== | ====Abstract==== | ||
| - | This was our second working session with Paul, after the one held in Brussels in 2014 on DIY supercapacitors from dead batteries. | + | This was our second working session with Paul, after the one held in Brussels in 2014 on [[michka: |
| We decided to focus this second session on the topic of microbial fuel cells (MFCs), a renewable electricity production device in which electrogenic bacteria digest organic matter in an anaerobic environment. | We decided to focus this second session on the topic of microbial fuel cells (MFCs), a renewable electricity production device in which electrogenic bacteria digest organic matter in an anaerobic environment. | ||
| - | Even though the MFCs power output are very low (typically 100 W/m3 [REF], or 50-100 microwatts for the 0.5L container of the Mudwatt kit [http:// | + | Even though the MFCs power output are very low (typically |
| * they may be made 100 % from municipal solid waste and renewable resources (mud, organic waste) which can be found everywhere ; | * they may be made 100 % from municipal solid waste and renewable resources (mud, organic waste) which can be found everywhere ; | ||
| * their operation can be quite continuous, compared to other renewables. | * their operation can be quite continuous, compared to other renewables. | ||
| - | After few prototyping sessions and a first workshop led on the topic, we got actual voltage and current measurements - even though they were quite low to be of any use. Exploring possible designs for a Power Management | + | After few prototyping sessions and a first workshop led on the topic, we got actual voltage and current measurements - even though they were quite low to be of any use. Exploring possible designs for a Power Harnessing |
| - | We therefore decided to start from a solid ground, the Mudwatt kit. Paul ordered three of them, which we set up. The one filled up with a smelly damped clay slush from the beach took-of on the second day of the Hackathon, and its LED was blinking twice every second on the end of the fifth day. The other two had not started yet at the end of our 3-days hackathon, but Mudwatt says they take at least 3-7 days to start [REF]. | + | We therefore decided to start from a solid ground, the Mudwatt kit. Paul ordered three of them, which we set up. The one filled up with a smelly damped clay slush from the beach took-of on the second day of the Hackathon, and its LED was blinking twice every second on the end of the fifth day. The other two had not started yet at the end of our 3-days hackathon, but [[https:// |
| - | While the Mudwatts were starting up, we worked on the PMS design and fabrication. We explored many different ways detailed below, including small surface-mount DC/DC boost converters, as well as through-hole-components-based circuits such as Joule Thiefs. Some further work needs to be done there to find the appropriate solution for the MFCs. | + | While the Mudwatts were starting up, we worked on the PHS design and fabrication. We explored many different ways detailed below, including small surface-mount DC/DC boost converters, as well as through-hole-components-based circuits such as Joule Thiefs. Some further work needs to be done there to find the appropriate solution for the MFCs. |
| We also worked on the PTS design and fabrication. The INA-219 current sensor connected to an Arduino Uno proved to be a just-accurate-enough good starting point, even though we had some voltage measurement issues. Paul also explored possible ways to make the data collected by the Arduino automatically updated and logged online, including the brand-new Arduino Cloud, and some older lower-level possibilities. | We also worked on the PTS design and fabrication. The INA-219 current sensor connected to an Arduino Uno proved to be a just-accurate-enough good starting point, even though we had some voltage measurement issues. Paul also explored possible ways to make the data collected by the Arduino automatically updated and logged online, including the brand-new Arduino Cloud, and some older lower-level possibilities. | ||
| Line 22: | Line 25: | ||
| Finally, Paul made an electrode out of graphite rods from an arts & crafts shop and an old bicycle stainless stell cable. | Finally, Paul made an electrode out of graphite rods from an arts & crafts shop and an old bicycle stainless stell cable. | ||
| - | Next steps include further monitoring of the Mudwatts, further research and prototyping on the PMS, more tests to improve the accuracy of the INA-219 current sensor, further exploration of Arduino-to-web connexions, as well as home-made MFC prototyping. | + | Next steps include further monitoring of the Mudwatts, further research and prototyping on the PHS, more tests to improve the accuracy of the INA-219 current sensor, further exploration of Arduino-to-web connexions, as well as home-made MFC prototyping. |
| ====Introduction==== | ====Introduction==== | ||
| Line 30: | Line 33: | ||
| We decided to focus this second session on the topic of microbial fuel cells (MFCs), a renewable electricity production device in which electrogenic bacteria digest organic matter in an anaerobic environment. | We decided to focus this second session on the topic of microbial fuel cells (MFCs), a renewable electricity production device in which electrogenic bacteria digest organic matter in an anaerobic environment. | ||
| - | Even though the MFCs power output are very low (typically 100 W/m3 [REF], or 50-100 microwatts for the 0.5L container of the Mudwatt kit [http:// | + | Even though the MFCs power output are very low (typically |
| * they may be made 100 % from municipal solid waste and renewable resources (mud, organic waste) which can be found everywhere ; | * they may be made 100 % from municipal solid waste and renewable resources (mud, organic waste) which can be found everywhere ; | ||
| * their operation can be quite continuous, compared to other renewables. | * their operation can be quite continuous, compared to other renewables. | ||
| Line 39: | Line 42: | ||
| * to set up Paul’s brand new Mudwatt kits, which are science education MFCs kits for kids. | * to set up Paul’s brand new Mudwatt kits, which are science education MFCs kits for kids. | ||
| * The reasoning behind this is to get some previously designed MFCs up and running, for the sake of self-confidence :) and to start our research on waste-based MFC from a solid ground. | * The reasoning behind this is to get some previously designed MFCs up and running, for the sake of self-confidence :) and to start our research on waste-based MFC from a solid ground. | ||
| - | * to reverse engineer the very simple and elegant power management | + | * to reverse engineer the very simple and elegant power harnessing |
| - | * The reasoning behind this is to get a previously designed | + | * The reasoning behind this is to get a previously designed |
| * to design a performance tracking system (PTS) for the Mudwatt or comparable MFCs, allowing to monitor in a relevant way their voltage and current outputs. | * to design a performance tracking system (PTS) for the Mudwatt or comparable MFCs, allowing to monitor in a relevant way their voltage and current outputs. | ||
| * This PTS will allow us to prototype many different designs from various waste sources, and see how they behave over the long-term, without going into time-consuming manual measurement protocols. | * This PTS will allow us to prototype many different designs from various waste sources, and see how they behave over the long-term, without going into time-consuming manual measurement protocols. | ||
| * make a graphite electrode out of graphite rods for art & crafts. | * make a graphite electrode out of graphite rods for art & crafts. | ||
| * This is a first step towards waste-sourced non-corroding electrode materials. | * This is a first step towards waste-sourced non-corroding electrode materials. | ||
| - | |||
| - | We owe a big thank you to Johann from the Flower Power Pot project [REF], who got us started on several of the tracks explored here. | ||
| ====1. Mudwatt kits==== | ====1. Mudwatt kits==== | ||
| ===1.1 Getting mud for the Mudwatt=== | ===1.1 Getting mud for the Mudwatt=== | ||
| + | |||
| + | {{: | ||
| We started the working session by walk to the seaside in Barry (Wales, UK), to collect: | We started the working session by walk to the seaside in Barry (Wales, UK), to collect: | ||
| * a kind of clay slush | * a kind of clay slush | ||
| + | {{: | ||
| + | {{: | ||
| * a more sandy slush | * a more sandy slush | ||
| + | {{: | ||
| + | {{: | ||
| + | |||
| … to feed the Mudwatts that Paul got previously. | … to feed the Mudwatts that Paul got previously. | ||
| Line 61: | Line 69: | ||
| ===1.2 Filling the Mudwatt=== | ===1.2 Filling the Mudwatt=== | ||
| - | We filled the Mudwatts first thing when we arrived at the workshop, following Mudwatt’s manual. | + | We filled the Mudwatts first thing when we arrived at the workshop, following |
| + | |||
| + | {{: | ||
| + | {{: | ||
| We labeled them as follows: | We labeled them as follows: | ||
| - | * the clay-slush one was called B (for “Boue”) | + | * the clay-slush one was called |
| - | * the sand-slush one was called S (for “Sable”) | + | * the sand-slush one was called |
| - | * the garden soil one was called J (for “Jardin”) | + | * the garden soil one was called |
| + | |||
| + | {{: | ||
| ===1.3 First performance measurements=== | ===1.3 First performance measurements=== | ||
| Line 78: | Line 91: | ||
| ===1.4 First LED blinks !=== | ===1.4 First LED blinks !=== | ||
| - | Mudwatt’s manual | + | [[https:// |
| Paul was performing a quick open-circuit voltage measurement on the Mudwatts in the middle of the afternoon of day 2, when he noticed that the open-circuit voltage across the B Mudwatt had jumped from several dozens mV to 0.4 V. | Paul was performing a quick open-circuit voltage measurement on the Mudwatts in the middle of the afternoon of day 2, when he noticed that the open-circuit voltage across the B Mudwatt had jumped from several dozens mV to 0.4 V. | ||
| Line 84: | Line 97: | ||
| He decided to plug the Hackerboard with its red LED on the B Mudwatt, to see what happened… and it blinked ! One time per second ! | He decided to plug the Hackerboard with its red LED on the B Mudwatt, to see what happened… and it blinked ! One time per second ! | ||
| - | The B Mudwatt, made from Barry’s bay clay-slush, was ready to the power the LED a little bit over 24 hours after setup ! | + | The B Mudwatt, made from Barry’s bay clay-slush, was ready to the power the LED around 30 hours after setup ! |
| ===1.5 Performance measurements=== | ===1.5 Performance measurements=== | ||
| Line 91: | Line 104: | ||
| We decided to use our freshly prototyped PTS (the INA219 current sensor on an Arduino Uno, see section 3 for details) on the B Mudwatt to see how much power was coming from out there. | We decided to use our freshly prototyped PTS (the INA219 current sensor on an Arduino Uno, see section 3 for details) on the B Mudwatt to see how much power was coming from out there. | ||
| + | |||
| + | {{: | ||
| Right after connexion, the load voltage was 1.03 V, and the current measured was around 10 mA, but decreasing very quickly. | Right after connexion, the load voltage was 1.03 V, and the current measured was around 10 mA, but decreasing very quickly. | ||
| Line 110: | Line 125: | ||
| By the evening of day 3 (around 6 pm), none of the other S & J MFCs were blinking. | By the evening of day 3 (around 6 pm), none of the other S & J MFCs were blinking. | ||
| - | ====2. Power Management | + | ====2. Power Harnessing |
| - | ===2.1 What is Mudwatt’s | + | ===2.1 What is Mudwatt’s |
| - | Mudwatt’s | + | Mudwatt’s |
| - | Info on the five-leads chip was hard to get. An old version of Mudwatt’s manual | + | Info on the five-leads chip was hard to get. An old version of [[https:// |
| - | Nowhere in the manual, nor in the old forum thread scavenged from Discs archives | + | Nowhere in the manual, nor in the old forum thread scavenged |
| - | By analysing thoroughly the situation, Paul noticed that the component had the same packaging and number of leads of a charge-pump I had seen in a paper from Meehan and Gao [REF], the Seiko 882-Z. | + | By analysing thoroughly the situation, Paul noticed that the component had the same packaging and number of leads of a charge-pump I had seen in [[https:// |
| - | We got the confirmation from Johann during our Skype call that it was this component that they used, as they named it at the end of their Instructable | + | We got the confirmation from Johann during our Skype call that it was this component that they used, as they named it at the end of [[http:// |
| However, Paul had already noticed that the production of the Seiko 882-Z seemed to be discontinued. | However, Paul had already noticed that the production of the Seiko 882-Z seemed to be discontinued. | ||
| Line 128: | Line 143: | ||
| We therefore needed to look for alternatives. | We therefore needed to look for alternatives. | ||
| - | ===2.2 First alternatives to Mudwatt’s | + | ===2.2 First alternatives to Mudwatt’s |
| - | Several scientific papers detail | + | Several scientific papers detail |
| - | - Meehan and Gao [REF] designed a PMS based on a Seiko 882-Z charge pump [https:// | + | - [[https:// |
| - | - Shantaram et al. [REF] designed a PMS based on a Maxwell 4F [@? TODO] supercap in series with the Max1797 DC/DC converter. | + | - [[https:// |
| - | - Thomas et al. [REF] designed a PMS based on a 1:20 < 1 V transformer, | + | - [[https:// |
| - | Meehan and Gao’s design is very interesting, | + | Meehan and Gao’s design is very interesting, |
| Shantaram et al.’s design seems quite promising too, as it connect directly the MFC to the DC/DC converter through a supercapacitor. | Shantaram et al.’s design seems quite promising too, as it connect directly the MFC to the DC/DC converter through a supercapacitor. | ||
| However, as we realized later on, their quite peculiar manganese-based MFC design with sacrificial electrode has a way higher output voltage, which allows to charge the supercapacitor without any charge pump. Our regular Mudwatt-like MFC design does not allow for such high voltages, and the capacitor charge will be stuck at the MFCs output, which is likely to be a few hundred mV at best. | However, as we realized later on, their quite peculiar manganese-based MFC design with sacrificial electrode has a way higher output voltage, which allows to charge the supercapacitor without any charge pump. Our regular Mudwatt-like MFC design does not allow for such high voltages, and the capacitor charge will be stuck at the MFCs output, which is likely to be a few hundred mV at best. | ||
| - | Thomas’ design is quite different than Meehan and Gao’s, using a small 1:20 coupled-inductor transformer instead of a charge pump. However, as we realized as Paul was cutting the PCB for the freshly ordered LTC3108 converter on his CNC, both recommended chips for the transformer | + | Thomas’ design is quite different than Meehan and Gao’s, using a small 1:20 coupled-inductor transformer instead of a charge pump. However, as we realized as Paul was cutting the PCB for the freshly ordered LTC3108 converter on his CNC, [[https:// |
| Anyway, we: | Anyway, we: | ||
| Line 147: | Line 162: | ||
| In addition to that, we: | In addition to that, we: | ||
| - | * assessed the use of a Beam robotics Solar Engine design | + | * assessed the use of a [[http:// |
| - | * explored in length the use of a Joule Thief circuit as a MFC PMS | + | * explored in length the use of a Joule Thief circuit as a MFC PHS. |
| - | ===2.3 Cutting a PCB for the LTC3108 DC/DC converter (Thomas et al. PMS)=== | + | ===2.3 Cutting a PCB for the LTC3108 DC/DC converter (Thomas et al. PHS)=== |
| - | The week before, Paul had ordered a small component called LTC3108, a small DC/DC converter featured in the power management | + | The week before, Paul had ordered a small component called LTC3108, a small DC/DC converter featured in the power harnessing |
| As it is a surface-mount component, it is not possible to use it in a traditional breadboard for prototyping, | As it is a surface-mount component, it is not possible to use it in a traditional breadboard for prototyping, | ||
| Line 165: | Line 180: | ||
| * sometimes, templates come up in large .zip files with components from a manufacturer, | * sometimes, templates come up in large .zip files with components from a manufacturer, | ||
| * open the template in Eagle, and check that it is the right one. | * open the template in Eagle, and check that it is the right one. | ||
| + | {{: | ||
| * if you are using, as we did, a fiber-glass support with a copper layer on top, keep in mind that were you cut, you are removing the copper, and therefore the electrical connexion. | * if you are using, as we did, a fiber-glass support with a copper layer on top, keep in mind that were you cut, you are removing the copper, and therefore the electrical connexion. | ||
| * export the G-code to Eagle’s plug-in connecting it to the CNC | * export the G-code to Eagle’s plug-in connecting it to the CNC | ||
| + | {{: | ||
| * beware that the G-code is defined in the right unit - metric or imperial system. | * beware that the G-code is defined in the right unit - metric or imperial system. | ||
| * make the CNC run | * make the CNC run | ||
| + | {{: | ||
| * this part of the process is quite technical, as the dimensions there are challenging Paul’s CNC sensitivity. Paul had to try out several times, and play with : | * this part of the process is quite technical, as the dimensions there are challenging Paul’s CNC sensitivity. Paul had to try out several times, and play with : | ||
| * the number of passes of the CNC on each cut | * the number of passes of the CNC on each cut | ||
| Line 176: | Line 194: | ||
| As we realized that we would not get the 1:20 transformer by the end of our working session, Paul switched to the realization of the Shantaram et al. circuit before he had a first fully working version of this PCB. | As we realized that we would not get the 1:20 transformer by the end of our working session, Paul switched to the realization of the Shantaram et al. circuit before he had a first fully working version of this PCB. | ||
| - | ===2.4 Building Shantaram et al.’s | + | ===2.4 Building Shantaram et al.’s |
| + | |||
| + | {{: | ||
| This was basically the same process as stated above, with a digression in updating Eagle to read the library files for the Maxim1797 layout, and getting compatibility issues with the CNC plug-in. | This was basically the same process as stated above, with a digression in updating Eagle to read the library files for the Maxim1797 layout, and getting compatibility issues with the CNC plug-in. | ||
| Last but not least, soldering the small surface-mount Maxim1797 and its tiny leads to the chip was quite a challenge, which Paul has adressed with years of hand-made-machines crafting experience. He drops a spot of superglue below the chip to paste it to the PCB, and then solders each lead with a tiny soldering iron tip. | Last but not least, soldering the small surface-mount Maxim1797 and its tiny leads to the chip was quite a challenge, which Paul has adressed with years of hand-made-machines crafting experience. He drops a spot of superglue below the chip to paste it to the PCB, and then solders each lead with a tiny soldering iron tip. | ||
| + | |||
| + | {{: | ||
| + | {{: | ||
| + | {{: | ||
| + | {{: | ||
| This being said, god bless through holes components ! | This being said, god bless through holes components ! | ||
| Line 192: | Line 217: | ||
| There were no 4 F supercapacitors with a leakage current of 28 microA on RS anyway, so we went for the Vishai one. | There were no 4 F supercapacitors with a leakage current of 28 microA on RS anyway, so we went for the Vishai one. | ||
| - | All the other components were found propoerly. | + | All the other components were found properly. |
| FYI, we did not tested the circuit before the end of our session. | FYI, we did not tested the circuit before the end of our session. | ||
| - | ===2.5 Beam robotics “Solar engine” | + | ===2.5 Beam robotics “Solar engine” |
| + | |||
| + | {{: | ||
| When discussing about a lower-tech charge pump circuit, Paul mentionned the Beam robotics circuits, which are often made of basic through-hole off-the-shelf components, and are powered by renewables. | When discussing about a lower-tech charge pump circuit, Paul mentionned the Beam robotics circuits, which are often made of basic through-hole off-the-shelf components, and are powered by renewables. | ||
| - | Paul identified a circuit which may be interesting for our application : the Solar Engine 1381 [http:// | + | Paul identified a circuit which may be interesting for our application : [[http:// |
| This very smart and simple circuit, which I took quite a bit of time to fully understand (lacking some basic transistor dynamics understanding), | This very smart and simple circuit, which I took quite a bit of time to fully understand (lacking some basic transistor dynamics understanding), | ||
| Line 209: | Line 236: | ||
| Anyway, we prototyped and tested the circuit (replacing the motor by a LED), and it worked perfectly well. A 2200 uF proved to be way to small to really see the circuit effect on a LED. We replaced it by a 10 F supercapacitor, | Anyway, we prototyped and tested the circuit (replacing the motor by a LED), and it worked perfectly well. A 2200 uF proved to be way to small to really see the circuit effect on a LED. We replaced it by a 10 F supercapacitor, | ||
| + | |||
| + | {{: | ||
| ===2.6 Through-hole-components-based charge pump=== | ===2.6 Through-hole-components-based charge pump=== | ||
| Line 214: | Line 243: | ||
| As we realized that none of our circuits will be completed during our Hackathon for various reasons - missing components, high voltage operation, I tried to go for a through-hole-components-based charge pump. | As we realized that none of our circuits will be completed during our Hackathon for various reasons - missing components, high voltage operation, I tried to go for a through-hole-components-based charge pump. | ||
| - | The Wikipedia page of charge pumps [REF] refered to a quite simple circuit which could be made of simple components. | + | The [[https:// |
| We were skeptical regarding the ability to design a charge pump operating at low voltages and low currents with basic through-hole components, but wanted to give it a try anyway. | We were skeptical regarding the ability to design a charge pump operating at low voltages and low currents with basic through-hole components, but wanted to give it a try anyway. | ||
| Line 222: | Line 251: | ||
| We should definitely go back to charge pumps design later anyway. | We should definitely go back to charge pumps design later anyway. | ||
| - | ====2.7 Joule Thief PMS==== | + | ====2.7 Joule Thief PHS==== |
| + | |||
| + | {{: | ||
| ===2.7.1 Literature review=== | ===2.7.1 Literature review=== | ||
| - | Joule Thief (JT) are simple through-hole-components-based converters which allow to power a 3.3 V LED from a used-up approx. 1 V AA cell. Its operation is pretty well described in this video [https:// | + | Joule Thief (JT) are simple through-hole-components-based converters which allow to power a 3.3 V LED from a used-up approx. 1 V AA cell. Its operation is pretty well described in [[https:// |
| - | Typical | + | According to [[http:// |
| When digging into literature, it seems that JT designers mostly focus on energy efficiency, at the expense of high current consumption. As our MFC provide both low-voltages and low-currents (0.3 V and 0.3 mA according to our latest measurements of the B Mudwatt), we have to focus on the design of a very low power JT. | When digging into literature, it seems that JT designers mostly focus on energy efficiency, at the expense of high current consumption. As our MFC provide both low-voltages and low-currents (0.3 V and 0.3 mA according to our latest measurements of the B Mudwatt), we have to focus on the design of a very low power JT. | ||
| - | Fortunately, | + | Fortunately, |
| Regarding the resistor connecting the cathode of the MFC to the feedback winding of the coil, we have to adjust - and probably reduce - its value to a point at which max LED brightness is achieved. Performing a Maximum Power Point tracking may be a good idea, according to Watson. Be careful when reducing, because if the resistor goes to zero : | Regarding the resistor connecting the cathode of the MFC to the feedback winding of the coil, we have to adjust - and probably reduce - its value to a point at which max LED brightness is achieved. Performing a Maximum Power Point tracking may be a good idea, according to Watson. Be careful when reducing, because if the resistor goes to zero : | ||
| Line 246: | Line 277: | ||
| * 30 AGW wire (thinner) has 0.104 ohm per foot resistance, when 24 AWG wire (thicker) has 1/4 of this resistance, so thicker wire may help. There are tables indicating wire resistance per diameter (AWG). | * 30 AGW wire (thinner) has 0.104 ohm per foot resistance, when 24 AWG wire (thicker) has 1/4 of this resistance, so thicker wire may help. There are tables indicating wire resistance per diameter (AWG). | ||
| * According to Watson, as the energy amount fed to the LED can be calculated as E = 0.5 * L * I^2, it is more important to reduce the resistance and increase the current (squared) by using less wire, than increase the inductance of the coil by increasing the number of turns. | * According to Watson, as the energy amount fed to the LED can be calculated as E = 0.5 * L * I^2, it is more important to reduce the resistance and increase the current (squared) by using less wire, than increase the inductance of the coil by increasing the number of turns. | ||
| - | * The feedback winding carries little current, it is only here to turn the transistor on and off, so its DC resistance is not critical. However, | + | * The feedback winding carries little current, it is only here to turn the transistor on and off, so its DC resistance is not critical. However, |
| * The target inductance of the coil value should be around 100-250 microH (milliHenris ?). With 24-26 AWG wires, this means 7 to 12 turns around 3/8-1/2 inches cores. A lower inductance will increase the oscillating frequency, which may then interfere with the AM frequency range. Moreover, the higher the frequency, the higher the losses in the toroid. | * The target inductance of the coil value should be around 100-250 microH (milliHenris ?). With 24-26 AWG wires, this means 7 to 12 turns around 3/8-1/2 inches cores. A lower inductance will increase the oscillating frequency, which may then interfere with the AM frequency range. Moreover, the higher the frequency, the higher the losses in the toroid. | ||
| - | * Air coils, which I liked for their simplicity, does not seem to be very appropriate, | + | |
| Regarding the transistor, we should pick one which can handle switching very high currents at very low voltage with very low losses. This means it has to: | Regarding the transistor, we should pick one which can handle switching very high currents at very low voltage with very low losses. This means it has to: | ||
| Line 269: | Line 300: | ||
| Watson also advised us to add a 10 uF capacitor across the + and - of the battery. In one of his posts, he has written that it may help the circuit oscillate. | Watson also advised us to add a 10 uF capacitor across the + and - of the battery. In one of his posts, he has written that it may help the circuit oscillate. | ||
| - | Other random and sometimes contradictory advice from Instructables | + | Other random and sometimes contradictory advice from [[http:// |
| * multiplying the number of turns by 5 | * multiplying the number of turns by 5 | ||
| * disconnecting the flat spot of the LED from the - of the battery, and connect it to the base of the transistor instead. | * disconnecting the flat spot of the LED from the - of the battery, and connect it to the base of the transistor instead. | ||
| - | There are many other designs to explore such as these ones [https:// | + | There are many other designs to explore such as [[https:// |
| ==2.7.2 First prototype and next steps== | ==2.7.2 First prototype and next steps== | ||
| + | |||
| + | {{: | ||
| While searching all the information mentionned above, we wanted to do a quick test with a basic JT design. | While searching all the information mentionned above, we wanted to do a quick test with a basic JT design. | ||
| - | We therefore built a simple one picking the circuit design | + | We therefore built a simple one picking the circuit design |
| Here are the main parameters of our JT : | Here are the main parameters of our JT : | ||
| Line 301: | Line 334: | ||
| It would also be good to see how a (super)capacitor behaves at the output of a JT: does it charge ? Maybe a diode in series with the capacitor might help, to avoid it discharging in the JT when its voltage oscillation reaches its low point ? | It would also be good to see how a (super)capacitor behaves at the output of a JT: does it charge ? Maybe a diode in series with the capacitor might help, to avoid it discharging in the JT when its voltage oscillation reaches its low point ? | ||
| - | If we go for several LEDs at the output, then we should read this piece from Watson | + | If we go for several LEDs at the output, then we should read [[http:// |
| ===2.8 Next steps=== | ===2.8 Next steps=== | ||
| - | More generally, we may need to get one step back, and look for general info on DC/DC converter, to understand the whole variety of architectures, | + | More generally, we may need to get one step back, and look for general info on DC/DC converter, to understand the whole variety of architectures, |
| We also sent an email to Mudwatt to ask how they were going to deal with the Seiko 882-Z being discontinued. Wait and see. | We also sent an email to Mudwatt to ask how they were going to deal with the Seiko 882-Z being discontinued. Wait and see. | ||
| Line 312: | Line 345: | ||
| ====3. Performance Tracking System==== | ====3. Performance Tracking System==== | ||
| + | |||
| + | {{: | ||
| ===3.1 Why INA219 current sensor ?=== | ===3.1 Why INA219 current sensor ?=== | ||
| - | When looking for a way to automatically measure the output of our Mudwatt and non-Mudwatt MFCs, Paul identified the INA219 current sensor for performance measurement - available on Adafruit | + | When looking for a way to automatically measure the output of our Mudwatt and non-Mudwatt MFCs, Paul identified the INA219 current sensor for performance measurement - available on [[https:// |
| - | During our e-mail exchanges with Johann, he had shared with us his bad experience with Arduino monitoring of the MFCs [REF]. | + | During our e-mail exchanges with Johann, he had shared with us [[https:// |
| His interpretation of the highly variable performance results he obtained was that the Arduino was at best not precise enough, and at worst interfering with electrical activity in the MFC. He encouraged us to drop Arduino measurement of the MFC, and look for other ways. | His interpretation of the highly variable performance results he obtained was that the Arduino was at best not precise enough, and at worst interfering with electrical activity in the MFC. He encouraged us to drop Arduino measurement of the MFC, and look for other ways. | ||
| Line 329: | Line 364: | ||
| The very first step of the set-up was to solder some pins on the INA219. | The very first step of the set-up was to solder some pins on the INA219. | ||
| - | Then, we connected it to an Arduino Uno following the very good doc on Adafruit’s website | + | Then, we connected it to an Arduino Uno following the very good doc [[https:// |
| We had to install the INA219 library provided by Adafruit on Arduino. | We had to install the INA219 library provided by Adafruit on Arduino. | ||
| Line 374: | Line 409: | ||
| ===4.1 Graphite electrode=== | ===4.1 Graphite electrode=== | ||
| + | |||
| + | {{: | ||
| Paul built a graphite electrode of out graphite rods we bought at The Works, an Arts & Crafts shop. | Paul built a graphite electrode of out graphite rods we bought at The Works, an Arts & Crafts shop. | ||
| + | |||
| + | {{: | ||
| He cut down the rods in smaller chunks, drilled them, and used an old bicycle stainless steel cable to assemble them like a collar. | He cut down the rods in smaller chunks, drilled them, and used an old bicycle stainless steel cable to assemble them like a collar. | ||
| + | |||
| + | {{: | ||
| + | {{: | ||
| Then, he tightened them up with a second bit of bicycle staineless steel cable (a choice of material advised by Johann, from the Flower Power pot project). | Then, he tightened them up with a second bit of bicycle staineless steel cable (a choice of material advised by Johann, from the Flower Power pot project). | ||
| + | |||
| + | {{: | ||
| A quick multimeter test showed that the overal resistance of the assembly was about 3 ohms. | A quick multimeter test showed that the overal resistance of the assembly was about 3 ohms. | ||
| Line 391: | Line 435: | ||
| We were quite happy to see one of the Mudwatt kits light up after two days of operation, and reaching a quite good frequency (2 blinks per second) at the end of the fifth day. | We were quite happy to see one of the Mudwatt kits light up after two days of operation, and reaching a quite good frequency (2 blinks per second) at the end of the fifth day. | ||
| - | We explored and open many tracks regarding the Power Management | + | We explored and open many tracks regarding the Power Harnessing |
| - | * Paul made some PCB’s for Thomas et al’s and Shantaram et al’s | + | * Paul made some PCB’s for Thomas et al’s and Shantaram et al’s |
| * We contacted Mudwatt for | * We contacted Mudwatt for | ||
| - | * We explored alternative | + | * We explored alternative |
| Regarding the Power Tracking System (PTS): | Regarding the Power Tracking System (PTS): | ||
| Line 406: | Line 450: | ||
| * Further prototyping and testing on the Joule Thief front; | * Further prototyping and testing on the Joule Thief front; | ||
| * Further reading on other DC/DC converting architectures; | * Further reading on other DC/DC converting architectures; | ||
| - | * Continuing the online discussions with Watson and Mudwatt related to the PMS; | + | * Continuing the online discussions with Watson and Mudwatt related to the PHS; |
| * Pursuing the INA-219 testing and fine tuning, especially on the load voltage front; | * Pursuing the INA-219 testing and fine tuning, especially on the load voltage front; | ||
| * Pursuing the online data monitoring and logging explorations, | * Pursuing the online data monitoring and logging explorations, | ||
| + | |||
| + | ====6. Acknowledgments==== | ||
| + | |||
| + | We owe a big thank you to : | ||
| + | * Johann from [[https:// | ||
| + | * [[http:// | ||
| + | * Keegan from Mudwatt who replied to our questions on the Mudwatt kit design. | ||
michka