How To Convert 24v to 9v so I can use Board of Education?

Im New To Micro

Hi,

For a project of mine, I'm needing a method for converting 24v DC to 9v DC which the board of education can handle. I'm curious what exactly I would need to do this?

Other components are hooked up to the battery like a motor which requires 24v, but since the board of education cannot handle that much voltage, I need a way to drop the voltage going to the Board of Education however, I do not want the voltage going to my motors to be effected any.

Leon

Use a National Semiconductor Simple Switcher:

http://www.national.com/en/power/simple_switcher/index.html

Im New To Micro

Leon wrote: »

Use a National Semiconductor Simple Switcher:

http://www.national.com/en/power/simple_switcher/index.html

Hmm just spent a couple of minutes trying it out and it seems like it has a lot of potential, however, it seems too complex or contains too many steps to get to a simple answer However, almost anything that's new seems that way at first so I may have to read up on how to actually use the thing later. Thanks though.

Mike Green

Dimension Engineering makes several switching regulators that are intended to replace standard linear 3-pin regulators. This one has an adjustable output voltage and can be set to produce 9V. You can make your own more cheaply using the National parts, but Dimension Engineering's is ready-to-go and not that expensive. I've used them

Im New To Micro

Mike Green wrote: »

Dimension Engineering makes several switching regulators that are intended to replace standard linear 3-pin regulators. This one has an adjustable output voltage and can be set to produce 9V. You can make your own more cheaply using the National parts, but Dimension Engineering's is ready-to-go and not that expensive. I've used them

Cool, thanks Mike, just what I needed I think. I just need to check to make sure it can handle 24v input from the datasheet.

Update: Yes it can handle 3-30v input! Just for anyone else wondering

Mike Green

The Dimension Engineering model I showed you is rated for 1A. If you need more than that, they have a 3A version as well. Also keep in mind that you may not need 9V. The Board of Education (BOE) is quite happy with 7.5V. It depends on what you have connected to the BOE.

Im New To Micro

Mike Green wrote: »

The Dimension Engineering model I showed you is rated for 1A. If you need more than that, they have a 3A version as well. Also keep in mind that you may not need 9V. The Board of Education (BOE) is quite happy with 7.5V. It depends on what you have connected to the BOE.

The only thing I need to power off it is the Board of Education which I believe only requires 1A or less? Or is it more? If so I may need to go with the 3A version. I hope it will be less than 1A as I already submitted my order haha, but I can probably cancel it if need be.

piguy101

Are you powering any servos/motors?

Im New To Micro

piguy101 wrote: »

Are you powering any servos/motors?

Motors why? I didn't know they even made 24v servos? lol

Mike Green

If you're using servos and powering them off the BOE's regulated 5V supply, remember that the 5V regulator is rated only at 1A and servos can draw peak currents of at least 1A each. If you're running the servos off the unregulated input supply, you're thinking of running them at 9V which will damage them. They're designed for supply voltages more like 4.5V, maybe as high as 7.2V or 7.5V although the higher voltages will shorten their lifetime due to increased arcing at the motor brushes. If you're running several servos off the unregulated input voltage, I'd use the Dimension Engineering 3A regulator and adjust the output to 7V, maybe as low as 6.5V. If you're running the servos off the regulated 5V supply, you may run into trouble if more than one servo runs into a significant mechanical load. The 5V regulator might be forced into a shutdown condition which would cause the Stamp to reset.

Im New To Micro

Mike Green wrote: »

If you're using servos and powering them off the BOE's regulated 5V supply, remember that the 5V regulator is rated only at 1A and servos can draw peak currents of at least 1A each. If you're running the servos off the unregulated input supply, you're thinking of running them at 9V which will damage them. They're designed for supply voltages more like 4.5V, maybe as high as 7.2V or 7.5V although the higher voltages will shorten their lifetime due to increased arcing at the motor brushes. If you're running several servos off the unregulated input voltage, I'd use the Dimension Engineering 3A regulator and adjust the output to 7V, maybe as low as 6.5V. If you're running the servos off the regulated 5V supply, you may run into trouble if more than one servo runs into a significant mechanical load. The 5V regulator might be forced into a shutdown condition which would cause the Stamp to reset.

lol people I'm not running or using servos in my application at all. All I need to be able to do is be able to send basic high/low signals from the board of education to different components in my application. I just need the same amount of normal power that one would have if they hooked it up to a 9v or 7.5v battery or power source.

I checked the Parallax website and they should a 9v adapter that was rated at 300mA I believe, so this device from Dimension Engineering should be more than enough if it will allow 1A.
Or the 7.5v version here which is at 1A: http://www.parallax.com/tabid/768/ProductID/73/Default.aspx

But if I can call and get them to replace it Monday with the 3A version I may do so since it's only $5 more, but overall it looks like what I'm getting should handle the job just fine I think.

BTW: Regarding the motors since I never mentioned much info on them in the beginning, they are regular 24v DC motors and on the plate it states they are rated for 10A. These are hooked directly in parallel with the 24v battery. They are electric wheelchair motors, so yes, fairly large motors. They will not have anything to do with the Parallax part of the application what so ever. Just a FYI

Mike Green

You should be fine with the 1A adjustable regulator. I'd still set the switching regulator for 7.5V rather than 9V since the difference is just dissipated as heat in the regulator on the BOE. Unless you hook up stuff to the Stamp that will draw a lot of current (like LEDs), the Stamp itself just draws a few tens of mA.

PJAllen

I'm New...,
I removed the BoE's "LDO" and replaced it with a 7805SR, they're similar to the DimEng devices.
It's on my "Cypherbot" which runs on batteries - so efficiency was my motivation.
(No pre-regulating linear regulators.)

PE -- Instructions

1. Remove heatsink.
   
2. Blob of solder on tip and heat all 3 pins at once, pulling up on reg/IC till it pulls out
   
3. Clear pcb holes for input and output with solder wick. It's hard to clear the middle/gnd (because of the ground copper), so leave it go
   
4. Place replacement device. With a blob of solder on tip and held to the ground/middle term on the pcb, push the new device down till it seats
   
5. Solder the input pin then clean up the solder on the ground pin, and then solder the output pin

PPE -
[ ! ]
Be that as it may, the/each BS2 has its very own on-board 5V reg powered from the BoE's "V_in" - not from the 5V out of the LDO (a/k/a "Vdd").
So, you'll be better served by an "off-board" solution.

...OK ?

PPPE -
At that rate, though, it seems a "waste"/under-utilisation using a BoE at all, you're not really using the BoE features. They're not inexpensive.

piguy101

I just realized that Dimension Engineering is based near me. I may have to drive there to check the place.