OPS - Energy Harvesting

1. OPS - Energy Harvesting • Name: Alex Phipps 12/13/2005 • Goals: • Mount solar cells to board. • Test PZT with resistive and PRC loads to confirm bimorph models and experimental data. • Key accomplishments. • Most parts have been soldered onto solar board. • Shengwen’s files have all been transferred and are functional. • Key issues • How to attach the solar cells to the board. • PZT bimorph beams no longer have the same impedance when measured. • Simulations are also difficult because the model doesn’t allow for Ropt to be used. • Next steps • Populate both boards. • Create test plan for new solar ICs. • New design has test pins for charge pump.

2. Action Items • Build Charge Pump Board. • Conduct a literature survey to determine if the charge pump is publishable. • Construct board for solar converter/controller. • Plan a paper around it. • Simulate PZT converter with Shengwen and Anurag to verify 6uW with Bimorph. • Simulate resistive loading and compare with experiments. • Talk with Erin about gold plating/ Wirebonding from IMG. • More solar cells available? • Software from Shenwen and familiarize with his work.

3. Action Item Progress • Build Charge Pump Board. • On hold while solar board is being constructed. • Construct board for solar converter/controller. • Board milled and most components have been added. • Simulate PZT converter with Shengwen and Anurag to verify 6uW with Bimorph. • Simulations predict more than 6uW of power using the Bimorph model. • Simulate resistive loading and compare with experiments. • Resistive loading seems to have changed for the Bimorph beams since the first data was taken. • Simulations cannot be easily altered to fit experimental results.

4. Action Item Progress • Talk with Erin about gold plating/ Wirebonding from IMG. • Probably will not be able to do it. Most likely will hire Al Ogden to complete the wirebonding. • More solar cells available? • IXYS has not responded to either of my emails. I also phoned in with little luck. • Software from Shenwen and familiarize with his work. • PZT and solar simulations finally both work on my account and backups are made.

5. Wirebonding • Al Ogden will probably have to do this. • Other options: • Gold plate whole board. • Cost and still need to wirebond. • Get gold plating “pen system” • Requires time to get system and cost of pens. • It will cost ~$52/hr and Al estimated 2-3hrs to do the whole job. • There is also the cost of silver epoxy, which should be relatively cheap.

6. PZT Testing • PZT tests conducted by Shengwen show the following:

7. PZT Testing • The problem for the PZT is now this: • The model that Anurag has for the bimorph gives a Ropt = 15.84k. Using this model in the cadence simulation with Ropt = 15.84k, resulted in an output of 32.7uW. When the bimorph beam was physically tested, the Ropt = 50k, and the maximum power output was only 13uW. • It is possible that the R1 measured to make the LEM model of the bimorph had some error. Since R1 is a major component in Re’, this could have a big effect on the Ropt. We want to edit Re’ so that Ropt is now equal to 50k. This means: • And since:

8. PZT Testing • We know that we must just change Re so that the impedance |ZTH| is 50k. However, due to the capacitance value that we found this is impossible. • The measured Ropt was done rather roughly, so Anurag and I decided to re-measure. • We found that Ropt had changed for the bimorphs and that the maximum power was no longer as high as it had been. • This will require more investigation.