DIY MC1466L power supply all finished. - Page 1
Forum section: electronics / projects

author: Jwillis
author_rank: Super Contributor
timestamp: April 09, 2018, 11:46:31 pm
content: YAAAY!!! I'm all finished my first bench top PSU .Unfortunately ,due to transformer limitations ,it's not perfect but I'm pretty proud of my accomplishment .I learned a lot doing this project.Although the MC1466L and MC1566L regulators has been discontinued, it is still available. I haven't burned up any yet despite all manners of failures gives me the impression that it's a pretty tough chip.The transformer would be better with a 500VA or better. I added a Constant current/voltage mode indicator and it works really well.Here's a few photos which include the lowest stable voltage/current , the full load test,and a full voltage test with a small motor.I haven't put it on the oscilloscope because of the transformer issue ,but the tests I have done have show it to be quite stable .I'm impressed.I'm still learning how to use KiCad so the diagram and art work were done with a simple drawing program. I'm sure that it could be compressed into a smaller package.As a side note ,the voltage pot internal connection was repaired with a home brew conductive glue made with copper powder ,graphite,PVA (carpenters glue) and water. I didn't feel like waiting for another one to arrived.

author: duak
author_rank: Super Contributor
timestamp: April 11, 2018, 08:40:49 pm
content: The MC1466 is an interesting chip and makes for a good bench supply. Kudos for building one up. Where did you get the MC1466 from?Lambda uses the MC1466 in their LP series. I have one and found that it has a problem when the output voltage is quickly turned down by the output voltage control P1. The problem is that P1's current rating can be exceeded when the actual output voltage is significantly greater than what the reference current from the MC1466 times P1's value tries to set it to ie., P1 is trying to sink current from the output by way of Q1's E-B junction. It's particulary bad when charging a battery - the power supply will discharge the battery and if the voltage control is set too low P1 will get hot and become intermittant or burn up. If P1 opens up, the output voltage goes to maximum, which can be very exciting.For the Lambda supply I added a TIP34C PNP power transistor connected as your Q1 with a 1 ohm collector resistor to help sink current. A better solution would be to somehow limit output current back to P1 but I couldn't think of a simple way to do it without adding a bunch of parts.Cheers,

author: Jwillis
author_rank: Super Contributor
timestamp: April 12, 2018, 06:16:15 pm
content: Q1 is used to to discharge C8 as you reduce the voltage.By the time the voltage gets to low to activate Q1, the amount of total energy in C8 is so small (some where around 0.000018 joules). Over a millisecond that converts to 0.018 Watts.You would have to turn the voltage down incredibly fast for that amount of energy to do any damage. But aside from the math, testing has confirmed that Q1 does indeed prevent damage to P1 voltage adjust .Even under full load.I don't intend on using this to charge batteries.Good battery chargers have voltage ,current and temperature sense along with balancing.Maybe I'll use it to power a battery charger sometime.It is unfortunate that these are no longer in production.I find them to be very stable and accurate .Plus the built in voltage reference brings voltage control to zero.I haven't found another regulator that will do this without external referencing . But according to Motorola restructuring ,many products were dropped in favor of communications.This included many linear applications. But you can still find the MC1466L and MC1566L on Ebay. I have a MC1566L on the way. Kind of fun to play with without worrying about burning them out with proper protection diodes and internal short protection.Mainly this was an exercise for me to learn and relearn things I had forgotten.You don't normally need this kind of information for civil engineering.But I'm happy to share a design that works.I find far to many simulator designs on the internet that work in theory but will not work in reality.But I'll leave that for another discussion entirely.Anyway ,give it a try and have fun with it.

author: multime
author_rank: Regular Contributor
timestamp: February 11, 2024, 10:36:58 pm
content: I am interested in building this power supply and i am wondering if the original poster or anyone else who may have built it would have a diagram showing the component side of the pcb.