ghostman11
Well-Known Member
hi guy's
doing a little bit of work on LG's mamouth rail project, and i am thinking of going daown the adjustable power supply route for the power suply that feeds the Rails.
Due to the H bridges (design of wich not finished) in some circumstances the actual max voltage availiable to the rails is around 10.5v (give or take) this is with a 12v supply going into the bridges,
for most situations this is fine and hunky dory, but we need the option to up it tempory now and then for when say we are using a couple of the big american loco's, theese seem to have much bigger motors and to realy get them powering up the steepest incline of the track we would like a couple more volts! so the idea is to use a LM150 voltage regulator in adjustable configuration, this will have a 20-24v input voltage(no final decision regarding transformer we are going to use but will have max 5A 24v), what i would realy like to do is use a digital potentiometer preferably with spi control to adjust the power rails for the bridge outputs.
this way we can automate when the extra voltage is applied. yes i could use a normal pot etc but would prefer to use digital pot under micro control. ive had a look on maxim site but got totaly lost with there parametric search. accuracy of the output dosnt have to be exstreme what we are looking for is to adjust the voltage upto a absolute max 0f around 16-17v wich should give a max bridge output of around 15v. +- 1-2v is fine.
so does anyone have any sugestions on wich digital pot would be best to use?
cheers jason
doing a little bit of work on LG's mamouth rail project, and i am thinking of going daown the adjustable power supply route for the power suply that feeds the Rails.
Due to the H bridges (design of wich not finished) in some circumstances the actual max voltage availiable to the rails is around 10.5v (give or take) this is with a 12v supply going into the bridges,
for most situations this is fine and hunky dory, but we need the option to up it tempory now and then for when say we are using a couple of the big american loco's, theese seem to have much bigger motors and to realy get them powering up the steepest incline of the track we would like a couple more volts! so the idea is to use a LM150 voltage regulator in adjustable configuration, this will have a 20-24v input voltage(no final decision regarding transformer we are going to use but will have max 5A 24v), what i would realy like to do is use a digital potentiometer preferably with spi control to adjust the power rails for the bridge outputs.
this way we can automate when the extra voltage is applied. yes i could use a normal pot etc but would prefer to use digital pot under micro control. ive had a look on maxim site but got totaly lost with there parametric search. accuracy of the output dosnt have to be exstreme what we are looking for is to adjust the voltage upto a absolute max 0f around 16-17v wich should give a max bridge output of around 15v. +- 1-2v is fine.
so does anyone have any sugestions on wich digital pot would be best to use?
cheers jason
you mean drive the adjust pin with a pwm signal? is that correct? yes i can see the advantage of doing that. all i need do is supply a pwm voltage via a transistor switch i guess. that would work better. i been looking at some datasheets for digital pots and most have a rubish voltage range with max's around 8v accross the resistor load so looks like i was weeing up the wrong tree 
