Status: Sheltering in place, we have plenty of food and supplies. COVID-19 cases are higher in our Gwinnett county than any other county in the state of Georgia.
Plans: Stay home and order everything online.
- 07:00 Up and sipp’n coffee.
- 08:00 Eating breakfast and making plans for the day.
- 09:00 Getting ready for church
- 10:00 Church service
- 12:00 NAP
- 14:00 Built AC source relay
- 15:00 Ordered Instacart groceries
- 16:00 Put groceries away
- 17:00 Eat’n dinner
- 18:00 Using the lawn mower as a vacuum.
- 19:00 Watching Cheers
- 22:00 Killing time
Narrative: I’ve built half a dozen AC source relays that have the task of keeping something powered while changing the power source. A UPS is great for keeping a computer alive, but what do you do if you have to change the UPS?
The answer is to put a relay with two power cords on it as the power source. That way EITHER cord can power the equipment. The relay has an AC coil so it activates when the second power cord has power. To date I’ve not had an issue with anything dropping out when the switching of the relay causes a short interruption in power. Most of my source relay boxes have fuses on the output line to protect the relay from arcing across the open contact.
To test projects like this I use an inherently limited power source. Usually a battery powered inverter that has just enough current to support the test. In this case I used a bench power supply that I can set the voltage and current limits. FYI, in most cases it didn’t matter that the source AC was a modified square wave inverter like the one below.
To keep the currents within reason I use 12 V for 100W or less, 300-600 Watts I like 24 volts and I use a whopping 48 Volts for 1000W and above. FYI 48V is very close to 60V for a lead acid battery. A great deal of care must be taken on choosing fuses for 60V battery banks. Automotive DC fuses are rated for 30 VDC and 3AG glass fuses are NOT rated for much above 60VDC at 7 Amps. High quality 15A, high voltage fuses are ceramic (Not glass) and filled with something to dissipate the arc when they open. (They are pricey too) High DC voltage fuse holders are like $10 each.
Feelings: According to our black families in our church that spoke up today, racism and prejudice are still rampant in the USA. Worse, they described their run-in’s with police often harassing them because of the color of their skin. They were very emotional describing their clashes with white people in authority not treating them or their children equally. The data supports some of their conversation today and they did not speak to the large number of black men belonging to gangs with guns in our cities.
Tomorrow: Monday, voting day. I’ve not applied for SS yet either.
Injuries: Arguments: Exercise: Feeling words: Travel: Noteworthy: Accmplishments: Purchases: Project: Theme: Engineering: Repairs: Pi News:
From the book “Triggers” by Marshall Goldsmith
Did I DMBT make my wife feel loved? Yes
Did I DMBT help my wife today? Yes
Did I DMBT be happy? Yes
*Did My Best To