HELP! 0-5.75VDC Voltage Controller w/ LED Bar Graph

[Miramax]

Hello hello! I'm First time poster, long time reader
I'm working on a circuit that will control a linear solenoid and display the amount of voltage being outputted onto a 10 LED Bar Graph.
The position of the solenoids ram is controlled by voltage, 5.75VDC @ 0.85A (It may be 5VDC, I need to confirm) sets the ram all the way out of the solenoid body, 0VDC and the ram is all the way back in the solenoid body. It looks like the LM317 regulator is going to do just what I need I picked some info out of the SparkFun Breadboard Power Supply schematic that uses the LM317
As far as the LED bar graph goes, the **broken link removed** looks like its going to do all the work! Its an IC that senses voltage and drives the LEDs based on this
What I have so far is below.. sorry its a little rough, I'm no Picasso or Tesla
**broken link removed**
PAD1 is the positive 12VDC from the lead-acid battery
PAD2 is negative from the battery
PAD3 is the variable 0-5.75VDC+ output to the solenoid
PAD4 is negative to the solenoid

I haven't figured the exact values on the caps and resistors quite yet..

The output voltage IS NOT to exceed 5.75VDC

I'm told, when external capacitors are used with any IC regulator it is good practice to add protection diodes to prevent the capacitors discharging back into the regulator in the event of abnormal operating conditions, like a sudden short circuit on the input or the output, or a back emf from an inductive load. That is the function of D1 and D2.

The LM3914 will drive the LED bar graph so we have a visual display of how many volts are at the output to the solenoid (PAD3)

R2 is the POT used to control the output voltage

C1 is a ceramic capacitor. This goes across the incoming power leads and smooth out any ripples before it enters the regulator
C2 is a polarized aluminum or tantalum capacitor. This will go across the output leads, and give a smooth buffer effect when the output is adjusted. I think I need to use larger capacitors for a larger buffer?

C3 and C4 are two capacitors keep things stable for the LM3914, C4 smooths out rapid changes and spikes in the input signal to the LM3914, and C3 keeps the levels from being distorted by spikes when LEDs turn on and off.

So far does this look in order? I know something here has to be wrong, or there is a more efficient way this needs to be done. Please, comments, questions, ideas, help a noob out

 

[audioguru]

Pin 6, pin 7 and pin 8 of the LM3914 as shown set its full scale input voltage to only 1.28V. Pin 6 and pin 7 need to have two resistors in series to ground with pin 8 connected between them to set the full scale voltage higher. Pins 7 and 8 are like an LM317 adjustable voltage regulator.

When all LEDs are on (2.0V red LEDs) and the supply voltage is 13.1V, the LM3914 will dissipate about 1110mW and will be very hot. Its absolute max dissipation is 1365mW but less in a hot car. A power resistor should be added in series with the group of LEDs to share the heat. Then the anodes of the group of LEDs need a bypass capacitor to ground.

 

[Miramax]

Thanks for the info! This is my first time using the LM3914
I'm thinking about junking the regulator and moving towards a PWM design because of heat and efficiency reasons. I stumbled across this PWM number that looks nice https://www.onsemi.com/PowerSolutions/product.do?id=CS2841BEBN8G
I know PWM is great for motor speed control.. I'm just curious how well PWM will work with a linear solenoid

 

[Miramax]

audioguru, something like this? https://www.national.com/images/pf/LM3914/00797001.pdf

 

[The Mad Professor]

Forest Mims or Penfold would be proud of that schematic Miramax.
Your information about the diodes is quite correct,
D3 - protects against reverse polarity of the input
D2 - ,, ,, back EMF from the solenoid
D1 - improves stabilty of the regulator output, it's a nice touch, not often found on many power supply circuits.

 

[Miramax]

Forest Mims or Penfold would be proud of that schematic Miramax.
Your information about the diodes is quite correct,
D3 - protects against reverse polarity of the input
D2 - ,, ,, back EMF from the solenoid
D1 - improves stabilty of the regulator output, it's a nice touch, not often found on many power supply circuits.

Thanks At least I have something going right

 

[audioguru]

The ON Semi IC is made to control the small voltage change in a power supply, not the huge amount of change that you need.

There are many ways to make wide-range PWM. A Cmos oscillator or 555 oscillator with a couple of diodes or a couple of opamps making a triangle wave and a comparator all work well. They can control a motor's speed, a light's brightness or the amount of power to your solenoid.

The schematic from the LM3914 datasheet shows two resistors setting the full-range reference voltage to about 5.33V and the current in the LEDs to about 10.6mA.

 

[Miramax]

After looking over the data sheet, that is the case
The 555 method sounds the way to roll, but it looks like I will need to do a good bit of homework on the subject..
If I do take the PWM road, wont I need something like a low pass filter before the 3914?

 

[audioguru]

The LM3914 will display the swing of from 0V to +5.75V of the PWM signal by lighting all LEDs unless a lowpass filter is added at its input.

 

[Miramax]

The LM3914 will display the swing of from 0V to +5.75V of the PWM signal by lighting all LEDs unless a lowpass filter is added at its input.

Thanks! Yeah I figured I would need a low pass filter in the works. I will do some more homework on PWM
If the PWM frequency is high enough the solenoid shouldn't care? However, since a solenoid is an inductor, the frequency does have to be considered... The problem will be similar to using PWM for motor control I hear

 

[audioguru]

A solenoid is an inductor. High freqencies produce less current in an inductor than lower frequencies or DC due to the reactance of the inductance. You would need to calculate the effect that is caused by the inductance and the frequency.

 

[Miramax]

Well! I have done a bit of homework on the ways of PWM and it looks like I'm going to junk the linear regulator idea and put a PWM circuit together using a 555 timer.
It looks like I will have to do some trial and error testing and see how the solenoid will react to PWM or if it even works with PWM for that matter..
I have not ran across any information in regards to controlling a linear solenoids position with PWM. The only thing I seem to find is motor speed control...
Anyone know where one might find some information on PWM and solenoids?
I don't know how to figure the inductance issue out, other than trial and error.. Thanks again

 

[Miramax]

You know, I guess this is more a stepper actuator or like, a linear servo than it is a solenoid.. I don't have the part in hand so I don't know exactly what it is I am working with yet... strange, yes I know..
But its beginning to look more and more like it must be controlled via PWM like your common servo, the regulator is going to be a complete no go.
Basically the idea is to have a shaft that can be positioned up or down with PWM. A servo, but instead of a rotational movement, it will be a rod/shaft moving up and down.. does that make any sense?
I will report back once I have a better idea of what I'm going to be working with
This is going to get interesting