Spyder Power Supply

[amazingalf]

Hello!

I'm currently working on a Spyder power supply build (8 x 9 volt outputs) and had a question regarding the output of the linear voltage regulator. I'm using the Weber WPDLXFMR power transformer and the schematic for the basic regulator by RG located on this geofx page: http://geofex.com/article_folders/oldspyder/oldspyder.htm

I'm using this voltage regulator: https://www.digikey.com/product-detail/en/stmicroelectronics/L78L09ACZ-TR/497-15651-1-ND/5253742

When I measure the output of the voltage regulator I'm reading 14.4 volts, not 9 volts. Should the output voltage of the regulator read high without a load? If so, is there a way to calculate what the correct output of the voltage regulator should be without a load? How could I go about creating a dummy load?

Any guidance here would be appreciated.

Thanks!

[davent]

My guess would be the regulator is flipped, 78L09 has the input on pin three where a 7809 has the input on pin one, easy to  mistake the orientation.
dave

[amazingalf]

davent, you nailed it. I switched the orientation after comparing the datasheets for the two regulators against the schematic from RG. I'm still reading a little hot at 9.1V. I compared this to a brand new 9 volt which reads at 9.1V as well, so I'm assuming this is an inaccuracy of my multi meter.

Thanks again for your help!!!

My next step is to design a pcb for this. I haven't been able to track one down for the spyder, but if anyone has seen one kicking around I'd love to know!

[PRR]

> I'm still reading a little hot at 9.1V.

It's 37 cents. You want perfection too?

Read the datasheet. The usual spec is +/-5%. So a "9V" can be 8.55V to 9.45V.

And yes, "1.5V" cells are closer to 1.56V (depending on additives) so a "9V battery" may be closer to 9.36V.